review of radicals math 017 intermediate algebra s. rook
TRANSCRIPT
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Review of Radicals
MATH 017
Intermediate Algebra
S. Rook
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Overview
• Section 7.1 in the textbook– Find square roots– Approximate roots– Find cube roots– Find nth roots
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Find Square Roots
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Find Square Roots
• Should be a review for numbers means “what number multiplied by itself gives you a”?
• What about the square root of a negative number?– Suppose we want to evaluate
• What number multiplied by itself gives you -4?There is none because the product of two numbers with the
same sign is always positive!
• Therefore, the square root of a negative number does NOT exist in the real number system
a
4
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Find Square Roots (Continued)
• Slightly different for variables– Consider
xxxx
)()( xxxx
2x
4x
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Find Square Roots (Continued)
• Thus: if a is divisible by 2• Perfect squares
– Should have the first ten perfect squares memorized
2aa xx
x x2 x x2 x x2 x X2
1 1 4 16 7 49 10 100
2 4 5 25 8 64
3 9 6 36 9 81
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Find Square Roots (Example)
Ex 1: Evaluate 82 4,,144,16,0 yx
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Approximate Roots
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Approximate Roots
• Most square roots will not evaluate to integers, but to irrational numbers
• Can approximate by “squeezing” the root between two perfect squares
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Approximate Roots (Example)
Ex 2: Approximate and then evaluate it using a calculator
51
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Find Cube Roots
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Find Cube Roots
• Should be a review for numbers means “what number multiplied by itself three times gives you a”?
• What about the cube root of a negative number?– Suppose we wish to evaluate
• What number multiplied by itself three times gives you -8?
-2
• Therefore, the cube root of a negative number exists in the real number system because the product of three negatives is negative
3 a
3 8
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Find Cube Roots (Continued)
• Slightly different for variables– Consider
3 xxxxxx
3 )()( xxxxxx
2x
3 6x
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Find Cube Roots (Continued)
• Thus: if a is divisible by 3• Perfect cubes
– Should have the first five perfect cubes memorized
33 aa xx
x x3 x x3
1 1 4 64
2 8 5 125
3 27
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Find Cube Roots (Example)
Ex 3: Evaluate 3 123 333 ,27,125,0 ba
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Find nth Roots
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Find nth Roots
• Should be a review for numbers means “what number multiplied by itself n times gives you a”?
• What about the nth root of a negative number?– Already saw that the cube root of a negative number exists
in the real number system exists while the square root of a negative number does not
– Can extend this to the general case• The product of an even number of negatives is positive
– Therefore, the even root of a negative number does NOT exist in the real number system
• The product of an odd number of negatives is negative– Therefore, the odd root of a negative number DOES exist in the
real number system
n a
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Find nth Roots (Continued)
• Slightly different for variables– Consider
4 xxxxxxxx
4 )()( xxxxxxxx
2x
4 8x
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Find nth Roots (Continued)
• Thus: if a is divisible by nnan a xx
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Find nth Roots (Example)
Ex 4: Evaluate 5 104 1644 32,,81,16 wz
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Summary
• After studying these slides, you should know how to do the following:– Evaluate square, cube, and nth roots– Approximate a root