8_applications of derivatives.pdf

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  • 8/10/2019 8_Applications of derivatives.pdf

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    FWWOCEFZC@BU @L JDXC\FZC\DU6

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    FWWOCEFZC@BU @L JDXC\FZC\DU

    :.6 Jdrcvftcvd fs f rftd ndfsurd

    Cl y > l(x) cs f lubetc`b l x, tmdbjx

    jy r l (x) rdprdsdbts tmd rftd-ndfsurd l y wctm rdspdet t` x.

    (f) rdprdsdbts)x('l`rjx

    jy

    7xx 7>

    tmd rftd `l emfbkd `l y w.r.t. x ft x > x7.

    (h) Cl y cberdfsds fs x cberdfsds, tmdbjx

    jycs p`sctcvd fbj cl y jderdfsds fs x cberdfsds, tmdb

    jx

    jycs bdkftcvd.

    (e) Nfrkcbfo E`st (NE) cs tmd cbstfbtfbd us rftd l emfbkd l t tfo e st wctm rdspdet t tmd bunhdr l ctdns

    pr`juedj ft fb cbstfbt.

    (j) Nfrkcbfo Xdvdbud (NX) cs tmd cbstfbtfbd us rftd l emfbkd l t`tfo rdvdbud wctm rdspdet t` tmd bunhdr

    `l ctdns s`oj ft fb cbstfbt.

    :.8 Zfbkdbts fbj b`rnfo

    (f) Z` lcbj tmd dquftc b l tmd tfbkdbt t` tmd eurvd y > l(x) ft tmd kcvdb p cbt W(x6, y

    6), pr`eddj fs ubjdr 1

    (c) Lcbjjx

    jylr`n tmd kcvdb dquftc`b y > l(x).

    (cc) Lcbj tmd vfoud ljx

    jyft tmd kcvdb p`cbt W (x

    6, y

    6), odt n >

    6

    6

    yy

    xxjx

    jy

    >>

    .

    (ccc) Zmd dquftc`b l tmd rdqucrdj tfbkdbt cs y y6> n (x x

    6).

    Cb pfrtceuofr, cl >

    6

    6

    yy

    xxjx

    jy

    >>

    j`ds b`t dxcst, tmdb tmd dquftc`b l tmd tfbkdbt cs x > x

    6.

    (h) Z` lcbj tmd dquftc b l tmd b rnfo t` tmd eurvd y > l(x) ft tmd kcvdb p`cbt W(x6, y

    6), pr`eddj fs ubjdr 1

    (c) Lcbjjx

    jylr`n tmd kcvdb dquftc`b y > l(x).

    (cc) Lcbj tmd vfoud ljx

    jyft tmd kcvdb p`cbt W(x

    6, y

    6).

    (ccc) Cl n cs tmd so pd l tmd b rnfo t` tmd kcvdb eurvd ft W, tmdb n >

    6

    6

    yy

    xxjx

    jy

    6

    >>

    .

    (cv) Zmd dquftc`b l tmd rdqucrdj b`rnfo cs y y6> n (x x

    6).

    Cb pfrtceuofr cl,

    6

    6

    yy

    xxjx

    jy

    >>

    > 7, tmdb tmd dquftc`b `l tmd b`rnfo ft W cs x > x

    69 fbj cl >

    6

    6

    yy

    xxjx

    jy

    >>

    j`ds b`t dxcst, tmdb tmd dquftc`b `l tmd b`rnfo ft W cs y > y6.

    Fbkod l cbtdrsdetc`b l tw` eurvds

    Zmd fbkod l cbtdrsdetc`b l tw` eurvds cs tmd fbkod hdtwddb tmd tfbkdbts t` tmd tw` eurvds ft tmdcr p`cbt

    `l cbtdrsdetc`b.

    Cl n6fbj n8frd tmd so`pds l tmd tfbkdbts t` tmd kcvdb eurvds ft tmdcr p`cbt l cbtdrsdetc`b W(x6, y6), tmdb

    tmd (feutd) fbkod qhdtwddb tmd eurvds cs kcvdb hy

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    FWWOCEFZC@BU @L JDXC\FZC\DU8

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    tfb q>86

    86

    nn6

    nn

    +-

    .

    Cb pfrtceuofr 1

    (c) cl n6n

    8> 6, tmdb eurvds frd sfcj t` eut rtm`k`bfooy.

    (cc) cl n6> n8, tmd eurvds t`uem dfem `tmdr.

    :.5 Cberdfscbk fbj jderdfscbk lubetc bs

    Cl l cs f rdfo vfoudj lubetc`b jdlcbdj cb fb cbtdrvfo J ( f suhsdt l X), tmdb l cs efoodj fb cberdfscbk lubetc`b

    cb fb cbtdrvfo J6(f suhsdt `l J) cll l`r foo x

    6, x

    8J

    6, x

    6? x

    8 l(x

    6) l(x

    8) fbj l cs efoodj f strcetoy

    cberdfscbk lubetc`b cb J6cll l`r foo x

    6, x

    8J

    6, x

    6? x

    8 l(x

    6) ? l(x

    8).

    Ucncofroy, l cs efoodj f jderdfscbk lubetc`b cb fb cbtdrvfo J8(f suhsdt l J) cll l`r foo x

    6, x

    8J

    8, x

    6? x

    8

    l(x6)l(x

    8) fbj l cs efoodj f strcetoy jderdfscbk lubetc b cb J

    8cll l r foo x

    6, x

    8J

    8, x

    6? x

    8l(x

    6) 2 l(x

    8).

    Cb pfrtceuofr, cl J6> J tmdb l cs efoodj fb cberdfscbk lubetc`b cll l`r foo x

    6, x

    8J, x

    6? x

    8

    l(x6) l(x8)9 fbj l cs efoodj strcetoy cberdfscbk lubetc`b cll l`r foo x6, x8J, x6? x8 l(x

    6) ? l(x

    8). Fbfo k`usoy, cl J

    8> J tmdb l cs efoodj f jderdfscbk lubetc`b cll l`r foo x

    6, x

    8J, x

    6

    ? x8 l(x

    6) l(x

    8)9 fbj l cs efoodj strcetoy jderdfscbk lubetc`b cll l`r foo x

    6, x

    8J, x

    6? x

    8 l(x

    6) 2

    l(x8).

    F lubetc`b wmcem cs dctmdr (strcetoy) cberdfscbk `r (strcetoy) jderdfscbk cs efoodj f (strcetoy) n`b`t`bce

    lubetc b.

    E`bjctc`bs l`r fb cberdfscbk r f jderdfscbk lubetc`b

    Zmd`rdn 6. Cl f lubetc`b l cs e`btcbu`us cb Yf, h^, fbj jdrcvfhod cb (f, h) fbj

    (c) l (x) 7 l`r foo x (f, h), tmdb l cs cberdfscbk cb Yf, h^

    (cc) l (x) 2 7 l`r foo x (f, h), tmdb l cs strcetoy cberdfscbk cb Yf, h^.

    Zmd`rdn 8. Cl f lubetc`b l cs e`btcbu`us cb Yf, h^, fbj jdrcvfhod cb (f, h) fbj

    (c) l (x) 7 l`r foo x (f, h), tmdb l cs jderdfscbk cb Yf, h^

    (cc) l (x) ? 7 l r foo x (f, h), tmdb l cs strcetoy jderdfscbk cb Yf, h^.

    Cb lfet, cl f lubetc`b l(x) cs e`btcbu`us cb Yf, h^, jdrcvfhod cb (f, h) fbj

    (c) l (x) 2 7 l r foo x(f, h) dxedpt l`r f lcbctd bunhdr l p`cbts wmdrd l (x) > 7, tmdb l(x) cs strcetoy

    cberdfscbk cb Yf, h^.

    (cc) l (x) ? 7 l r foo x(f, h) dxedpt l`r f lcbctd bunhdr l p`cbts wmdrd l (x) > 7, tmdb l(x) cs strcetoyjderdfscbk cb Yf, h^.

    :.: Nfxcnf fbj Ncbcnf

    Cl l cs f rdfo vfoudj lubetc`b jdlcbdj b J (suhsdt l X) tmdb

    (c) l cs sfcj t` mfvd f nfxcnun vfoud cb J, cl tmdrd dxcsts f p`cbt x > e cb J suem tmft l(e) l(x)

    l`r foo x J. Zmd bunhdr l(e) cs efoodj tmd (fhs`outd) nfxcnun vfoud `l l cb J fbj tmd p`cbt e cs

    efoodj p`cbt l nfxcnf l l cb J.

    (cc) l cs sfcj t` mfvd f ncbcnun vfoud cb J, cl tmdrd dxcsts f p cbt x > j cb J suem tmft l(j) l(x) l`r foo

    x J. Zmd bunhdr l(j) cs efoodj tmd (fhs`outd) ncbcnun vfoud l l cb J fbj tmd p`cbt j cs efoodjp cbt l ncbcnf l l cb J.

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    (f) O efo nfxcnf fbj o`efo ncbcnf

    Cl l cs f rdfo vfoudj lubetc`b jdlcbdj b J (suhsdt l X), tmdb

    (c) l cs sfcj t` mfvd f o efo (`r rdoftcvd) nfxcnf ft x > e (cb J) cll tmdrd dxcsts f p`sctcvd rdfo bunhdr

    jsuem tmft l(e)l(x) l`r foo x cb (e j, e +j) c.d. l(e)l(x) l`r foo x cb tmd cnndjcftd bdckmh`urm``j`l e, fbj e cs efoodj p`cbt l o`efo nfxcnf fbj l(e) cs efoodj o`efo nfxcnun vfoud.

    (cc) l cs sfcj t` mfvd o efo (`r rdoftcvd) ncbcnf ft x > j(cb J) cll tmdrd dxcsts s`nd p sctcvd rdfo bunhdrjsuem tmft l(j) l(x) l`r foo x (j j, j + j) c.d. l(j)l(x) l`r foo x cb tmd cnndjcftd bdckmh`urm``j`l j, fbj j cs efoodj p`cbt l o`efo ncbcnf fbj l(j) cs efoodj o`efo ncbcnun vfoud.

    Kd`ndtrcefooy, f p`cbt e cb tmd j`nfcb l tmd kcvdb lubetc`b l cs f p`cbt l o`efo nfxcnf r o`efo

    ncbcnf fee`rjcbk fs tmd krfpm l l mfs f pdfi r tr`ukm (efvcty) ft e.

    (ccc) f p`cbt (cb J) wmcem cs dctmdr f p cbt l o efo nfxcnf r f p`cbt `l o`efo ncbcnf cs efoodj fb

    dxtrdnd p`cbt, fbj tmd vfoud l tmd lubetc`b ft tmcs p`cbt cs efoodj fb dxtrdnd vfoud.

    (h) Erctcefo ( r turbcbk) p`cbt

    Cl l cs f rdfo vfoudj lubetc`b jdlcbdj `b J (suhsdt `l X), tmdb f p`cbt e (cb J) cs efoodj f erctcefo

    (`r turbcbk r stftc`bfry) p`cbt l l cll l cs jclldrdbtcfhod ft x > e fbj l (e) > 7.

    (e) W`cbt l cblodetc`b

    F p`cbt W(e, l(e)) b tmd eurvd y > l(x) cs efoodj f p`cbt l cblodetc`b cll b bd scjd l W tmd eurvd ocds

    hdo w tmd tfbkdbt ft W fbj b tmd tmdr scjd ct ocds fh`vd tmd tfbkdbt ft W. Zmus, f p`cbt wmdrd tmd eurvd

    er`ssds tmd tfbkdbt cs efoodj f p`cbt l cblodetc`b.

    Zmd`rdn. F lubetc`b l (`r tmd eurvd y > l(x)) mfs f p`cbt l cblodetc b ft x > e cll l (e) > 7, l (e) > 7 fbj

    l (e) 7.

    (j) [`ricbk ruods l`r lcbjcbk (fhs outd) nfxcnun fbj ncbcnun

    Cl f lubetc`b l cs jclldrdbtcfhod cb Yf, h^ dxedpt (p`sschoy) ft lcbctdoy nfby p`cbts, tmdb t` lcbj (fhs`outd)

    nfxcnun fbj ncbcnun vfouds fj`pt tmd l`oo`wcbk pr`edjurd 1

    (c) Dvfouftd l(x) ft tmd p cbts wmdrd l (x) > 7

    (cc) Dvfouftd l(x) ft tmd p cbts wmdrd jdrcvftcvd lfcos t` dxcst.

    (ccc) Lcbj l(f) fbj l(h).

    Zmdb tmd nfxcnun l tmdsd vfouds cs tmd fhs outd nfxcnun fbj ncbcnun l tmdsd vfouds cs tmd fhs outd

    ncbcnun l tmd kcvdb lubetc`b l.

    (d) [`ricbk ruods t` lcbj p`cbts l o efo nfxcnf fbj ncbcnf

    6. O`eftd tmd p cbts wmdrd tmd kcvdb lubetc`b l cs ocidoy t` mfvd dxtrdnd vfouds 1

    (c) Zmd p cbts wmdrd tmd jdrcvftcvd lfcos t dxcst.

    (cc) Zmd turbcbk (erctcefo) p cbts c.d. tmd p`cbts wmdrd tmd jdrcvftcvd cs zdr .

    (ccc) Dbj p`cbts l tmd j`nfcb cl l cs jdlcbdj cb f eo sdj cbtdrvfo Yf, h^.

    Zmdsd frd tmd boy p`cbts wmdrd l nfy mfvd dxtrdnd vfouds, odt e hd fby bd suem p`cbt.

    8. Cl l (e) j`ds b t dxcst hut l dxcsts cb bdckmh`urm` j l e, tmdb tmd l oo`wcbk tfhod jdserchds tmd

    hdmfvc ur l tmd lubetc b l ft e 1

    x sockmtoy ? e sockmtoy 2 e Bfturd l p`cbt

    l '(x) + vd vd Nfxcnf

    l '(x) vd + vd Ncbcnf

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    5. Cl e cs f turbcbk p cbt c.d. l (e) dxcsts fbj l (e) > 7. Odt b8 hd tmd snfoodst p`sctcvd cbtdkdr suem

    tmft l(b)(e) 7, tmdb tmd l`oo`wcbk tfhod jdserchds tmd hdmfvc`ur l tmd lubetc`b l ft e 1

    b sckb `l l(b)(e) Bfturd `l tmd turbcbk p`cbt e

    `jj + vd r vd Bdctmdr nfxcnf b`r ncbcnf

    dvdb + vd Ncbcnfdvdb vd Nfxcnf

    Fotdrbftcvdoy, cl ct cs jcllceuot t` lcbj tmd jdrcvftcvds l mckmdr rjdr tmdb tmd l`oo`wcbk tfhod jd-

    serchds tmd hdmfvc`ur l tmd lubetc b l ft e 1

    x sockmtoy ? e sockmtoy 2 e Bfturd l tmd turbcbk p`cbt

    l '(x) + vd vd Nfxcnf

    l '(x) vd + vd Ncbcnf

    l '(x) + vd + vd Bdctmdr nfxcnf b`r ncbcnf

    l '(x) vd vd Bdctmdr nfxcnf b`r ncbcnf

    :. Zmd l oo`wcbk tfhods jdserchd tmd hdmfvc ur ft tmd dbj p cbts 9

    Odt dbj p`cbt f.

    x sockmtoy 2 f Bfturd l p`cbt

    l '(x) + vd Ncbcnf

    l '(x) vd Nfxcnf

    Xckmt dbj p`cbt h.

    x sockmtoy ? h Bfturd l p`cbt

    l '(x) + vd Nfxcnf

    l '(x) vd Ncbcnf

    4. Lcbfooy, t` lcbj tmd fhs outd nfxcnun r fhs`outd ncbcnun l f lubetc`b l cb eo`sdj cbtdrvfo Yf, h^

    9 lcbj tmd vfouds `l l ft tmd p cbts `l foo tmd tmrdd eftdk`rcds ocstdj fh`vd. Zmd nfxcnun `l tmdsd vfouds cs

    tmd fhs outd nfxcnun fbj tmd ncbcnun l tmdsd vfouds cs tmd fhs outd ncbcnun l tmd lubetc b l cb Yf, h .

    (l) L`r prfetcefo pr hodns b nfxcnf fbj ncbcnf

    Cl f lubetc`b cs e`btcbu`us cb fb pdb cbtdrvfo (f, h) fbj ct mfs boy bd dxtrdnd p`cbt cb (f, h), tmdb ct csf p`cbt l fhs`outd nfxcnf r f p`cbt l fhs`outd ncbcnf fee`rjcbk fs ct cs f p`cbt l o efo nfxcnf r f

    p cbt l o efo ncbcnf.

    :.4 Fppr`xcnftc bs

    Odt y > l(x) hd f lubetc`b `l x fbj jx hd f snfoo emfbkd cb tmd vfoud l x fbj jy hd tmd e`rrdsp`bjcbk

    emfbkd cb tmd vfoud l y, tmdb jx >jx

    jyjx.

    * U`nd cnp`rtfbt tdrns

    Fhs`outd drr`r.Zmd cberdndbtjx cb x cs efoodj tmd fhs`outd drr`r cb x.

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    FWWOCEFZC@BU @L JDXC\FZC\DU4

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    Dx.6 Zmd rfjcus `l fb fcr huhhod cs cberdfscbk ft tmd rftd `l8

    6en/s. Ft wmft rf td cs tmd v`ound

    `l tmd huhhod cberdfscbk wmdb tmd rfjcus cs 6 en 0

    U`o. Odt r en hd tmd rfjcus `l fb fcr huhhod fbj \ en 5hd cts v`ound. Zmdb,

    \ >5

    : pr5 ..........(c)

    Ct cs kcvdb tmftjt

    jr>

    8

    6en/s

    B`w, lr`n (c), wd mfvd

    jt

    j\> :pr8

    jt

    jr> :pr8

    8

    6> 8pr8

    [mdb r > 6 en,

    jt

    j\> 8p(6)8> 8pen5/s

    Zmus, tmd rftd l emfbkd l v ounds l tmd fcr huhhod cs 8pen5/s.

    Dx.8 F hfoo``b, wmcem fowfys rdnfcbs spmdrcefo `b cbloftc`b, cs hdcbk cbloftdj hy punpcbk cb 377

    euhce edbtcndtdrs `l kfs pdr sde`bj. Lcbj tmd rftd ft wmcem tmd rfjcus `l tmd hfoo``b

    cberdfsds wmdb tmd rfjcus cs 64 en.

    U`o. Odt r en jdb`td tmd rfjcus l tmd spmdrcefo hfoo``b fbj \ hd cts v`ound. Zmdb,

    \ >5

    :pr5 ........(c)

    Ct cs kcvdb tmft jt

    j\> 377 en5/s

    Lr`n (c), wd mfvd

    jt

    j\> :pr8

    jt

    jr

    jt

    jr> 8r:

    377

    p> 8r

    884

    p

    [mdb r > 64 en,

    jt

    jr> 8)64(

    884

    p>

    p6

    >88

    ;en/s

    Zmus, tmd rftd ft wmcem tmd rfjcus l tmd hfoo` b cberdfsds cs88

    ;en/s, wmdb r > 64 en.

    Dx .5 Lcbj tmd odfs t vf oud `l f suem tmft tmd lube tc`b l kcvdb hy l(x) > x8+ fx + 6 cs strcetoy

    cberdfscbk cb (6, 8).

    U`o. Mdrd, l (x) > 8x + f

    B`w, 6 ? x ? 8 8 ? 8x ? :

    8 + f ? 8x + f ? : + f ....(6)

    B`w, l(x) cs fb cberdfscbk lubetc b, s` l (x) 2 7 l r x(6, 8)

    8x + f 2 7 l`r x (6, 8) 7 ? 8x + f l`r x (6, 8)

    U@O\DJ WX@HODUN

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    FWWOCEFZC@BU @L JDXC\FZC\DU x8 x + 6 cs bdctmdr strcetoy cberdfscbk b`r strcetoy

    jderdfscbk cb (6, 6).

    U`o. [d mfvd, l(x) > x8 x + 6

    l (x) > 8x 6

    Zmd erctcefo vfoud l l(x) cs8

    6

    Efsd 6[mdb 6 ? x ?8

    6

    Cb tmcs efsd, 6?x?8

    6 5?8x 6?7

    l (x) ? 7

    Zmus, l(x) cs jderdfscbk l`r 6 ? x ?8

    6

    Efsd 8 [mdb8

    6? x ? 6

    Cb tmcs efsd,8

    6? x ? 6 6 ? 8x ? 8 7 ? 8x 6 ? 6

    Mdbed, l (x) 2 7

    U`, l(x) cs cberdfscbk l`r8

    6? x ? 6

    U`, cb tmd cbtdrvfo (6, 6), l(x) cs bdctmdr cberdfscbk b`r jderdfscbk.

    Dx.4 Lcbj tmd p`cbts `b tmd eurvd y > x5ft wmcem tmd so`pd `l tmd tfbkdbt cs dqufo t` tmd y-

    e``rjcbftd `l tmd p`cbt.

    U`o. Odt tmd p`cbt l tfbkdbey hd (x6, y

    6).

    Zmd, so`pd l tmd tfbkdbt ft (x6, y

    6) cs kcvdb Y ^

    6

    6

    xx8

    xx

    x5cswmcem,jx

    jyhy >

    >

    c.d., 86x5 .

    Ucbed, tmd so`pd cs kcvdb t` hd dqufo t` y6,wd mfvd

    86x5 > y6 ......(6)

    Fs (x6, y

    6) ocds `b tmd eurvd y > x5, wd mfvd

    y6> 56x .......(8)

    Lr`n (6) fbj (8), wd mfvd

    86x5 >

    56x

    x6> 7, 5 fbj s y

    6> 75> 7 r y

    6> 55> 8;

    Zmus, tmd rdqucrdj p`cbts frd (7, 7) fbj (5, 8;).

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    Dx.< Lcbj tmd dquftc`b l tmd b`rnfo ft tmd p`cbt (fn8, fn5) l`r tmd eurvd fy8> x5.

    U`o. Uo`pd l tmd tfbkdbt t` tmd eurvd fy8> x5ft tmd p`cbt (fn8, fn5) cs kcvdb hy

    )fn,fn(

    58jx

    jy

    Kcvdb fy8> x5

    [d mfvd, 8fyjx

    jy> 5x8

    jx

    jy>

    fy8

    x5 8

    )fn.fn(

    58jx

    jy

    >

    f8

    55

    :8

    fn

    nf>

    8

    n5

    _Uo pd l tmd b rnfo t tmd eurvd ft (fn8, fn5) cs n5

    8.

    Mdbed, tmd dquftc`b l tmd b`rnfo ft tmd p`cbt (fn8, fn5) t` tmd eurvd fy8> x5cs

    y fn5> n5

    8(x fn8)

    c.d., 5ny 5fn:> 8x + 8fn8

    c.d., 8x + 5ny fn8(8 + 5n8) > 7

    Dx.; F ecreuofr ndtfo poftd dxpfbjs ubjdr mdftcbk s` tmft cts rfjcus cberdfsds hy 8%. Lcbj tmd

    fppr`xcnftd cberdfsd cb tmd frdf l tmd poftd cl tmd rfjcus l tmd poftd hdl`rd mdftcbk cs 67 en.

    U`o. Odt r en hd tmd rfjcus l tmd ecreuofr poftd fbj F hd cts frdf. Zmdb, F > pr8

    jrjF

    > 8prKcvdb r > 67 en (hdl`rd mdftcbk)

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  • 8/10/2019 8_Applications of derivatives.pdf

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  • 8/10/2019 8_Applications of derivatives.pdf

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  • 8/10/2019 8_Applications of derivatives.pdf

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    FWWOCEFZC@BU @L JDXC\FZC\DU66

    www.tmcbicct.cb

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    jcndbsc`bs l tmd wcbj`w s` tmft nfxcnun ockmt dbtdrs tmr`ukm tmd wcbj`w. YE.H.U.D. 8775^

    V.68 F pfrtceod n`vds fo`bk tmd eurvd y >5

    8x5+ 6. LCbj tmd p`cbts `b tmd eurvd ft wmcem y-e``rjcbftd cs

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    h x hd nfxcnun 0 Fos` lcbj tmd nfxcnun v ound l tmd h`x. YE.H.U.D. 8775^

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    surlfed frdf ft tmd cbstfbt wmdb cts rfjcus cs 4 en. YE.H.U.D. 877:^

    V.86 Lcbj tmd cbtdrvfos cb wmcem lubetc`b l(x) > 8x5

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    www.tmcbicct.cb

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    V.56 Um`w tmft tmd nfxcnun v`ound l tmd eyocbjdr wmcem efb hd cbserchdj cb f spmdrd l rfjcus 54 cs 477pen5. YE.H.U.D. 8774^

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    FWWOCEFZC@BU @L JDXC\FZC\DU65

    www.tmcbicct.cb

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    V.

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    FWWOCEFZC@BU @L JDXC\FZC\DU6:

    www.tmcbicct.cb

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