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Test 1 2nd 9 weeks Review 1 Functions
What is a function? A rule Domain: the set of all inputs for the function Range: the set of all possible values of f(x) as x varies throughout the domain (set of outputs/ set of outcomes) Finding the domain of a function. What do you look for? *Domain excludes x-‐values that result in division by zero. Ex. 𝑓 𝑥 = !
!!!!
𝑥! − 4 ≠ 0 𝑥! ≠ 4 𝑥 ≠ ±2 Domain would be all real numbers x except for 2 and -‐2. −∞,−2 ∪ −2,2 ∪ 2,∞ *Domain excludes x-‐values that result in even roots of negative numbers. Ex. 𝑓 𝑥 = 𝑥 𝑥 ≥ 0 𝑐𝑎𝑛𝑛𝑜𝑡 𝑏𝑒 𝑛𝑒𝑔𝑎𝑡𝑖𝑣𝑒 0,∞ Evaluating Functions Input Output Equation 𝑥 𝑓(𝑥) 𝑓 𝑥 = 3 − 2𝑥
Example: Find the following function values. 𝑓 −1 , 𝑓 0 , 𝑎𝑛𝑑 𝑓(2) Solution: 𝑓 −1 = 3 − 2 −1 = 3 + 2 = 5 𝑓 0 = 3 − 2 0 = 3 − 0 = 3 𝑓 2 = 3 − 2 2 = 3 − 4 = −1
Test 1 2nd 9 weeks Review 2 Functions
Section 1.8 : Combining Functions Algebra of Functions Let f and g be functions with domains A and B, respectively. Then: 𝑓 + 𝑔 𝑥 = 𝑓 𝑥 + 𝑔 𝑥 The domain is 𝐴 ∩ 𝐵 𝑓 − 𝑔 𝑥 = 𝑓 𝑥 − 𝑔 𝑥 The domain is 𝐴 ∩ 𝐵 𝑓𝑔 𝑥 = 𝑓(𝑥) ∙ 𝑔(𝑥) The domain is 𝐴 ∩ 𝐵 !!
𝑥 = ! !! !
The domain is 𝐴 ∩ 𝐵 𝑠𝑢𝑐ℎ 𝑡ℎ𝑎𝑡 𝑔(𝑥) ≠ 0 Composition of Functions 𝑓 ∘ 𝑔 𝑥 = 𝑓 𝑔 𝑥 The domain of 𝑓 ∘ 𝑔 is the set of all x in the domain of g such that g(x) is in the domain of f.
Test 1 2nd 9 weeks Review 3 Functions
Section 1.9: Inverse Functions Horizontal Line Test for Inverse Functions A function f has an inverse function if and only if no horizontal line intersects the graph of f at more than one point. One-‐to-‐One Functions A function f is one-‐to-‐one if each value of the domain (inputs) corresponds to exactly one value of the range (outputs). A function f has an inverse function if and only if f is 1-‐1. Inverse Functions Let f be a one-‐to-‐one function with domain A and range B. Then its inverse function f-‐1 has domain B and range A defined by:
𝑓!! 𝑦 = 𝑥 𝑖𝑓 𝑎𝑛𝑑 𝑜𝑛𝑙𝑦 𝑖𝑓 𝑓 𝑥 = 𝑦 Verifying Inverse Functions Cancellation properties: 𝑓 𝑓!! 𝑥 = 𝑥 𝑎𝑛𝑑 𝑓!! 𝑓 𝑥 = 𝑥 If 𝑓 𝑔(𝑥) = 𝑥 𝑎𝑛𝑑 𝑔 𝑓 𝑥 = 𝑥 then 𝑓 𝑎𝑛𝑑 𝑔 are inverses of each other. Finding an Inverse Function of a One-‐to-‐One Function (algebraically) 1. Replace f(x) with y. 2. Interchange the roles of x and y. 3. Solve for y. 4. Replace y with 𝑓!! 𝑥 .
Test 1 2nd 9 weeks Review 4 Functions
Study Questions Definitions on test: 1. A function is even if __________________. 2. A function is odd if ___________________. 3. 𝑓 and 𝑔 are inverses if ___________________. 4. A function is 1-‐1 if _______________________. 5. If a function is even then it is symmetric about the ___________________. 6. If a function is odd then it is symmetric about the ______________.
Given 𝑓 𝑥 = 3𝑥! + 4𝑥 and 𝑔 𝑥 = 𝑥 − 2, evaluate the following: 1. 𝑓 4 2. 𝑓 −2𝑥 3. 𝑓(𝑎 + 5) 4. 𝑔 −6 5. 𝑔 3𝑎 + 5 6. 𝑔 8𝑥! + 4 7. 𝑓 + 𝑔 𝑥 8. 𝑔 − 𝑓 𝑥 9. 𝑓𝑔 𝑥 10. (!
!)(𝑥)
11. 𝑓 ∘ 𝑔 𝑥 12. 𝑔 ∘ 𝑓 𝑥 13. 𝑓 ∘ 𝑔 2 14. 𝑓 ∘ 𝑓 𝑥 15. State the domain of 𝑓 𝑥 16. State the domain of 𝑔 𝑥 17. State the domain of #10
Test 1 2nd 9 weeks Review 5 Functions
Tell if the following functions are even, odd or neither. State the symmetry. 1. 𝑦 = 5𝑥! + 2𝑥 2. 𝑦 = 3𝑥! + 2𝑥! − 5 3. 𝑦 = 8𝑥! − 3𝑥! 4. 𝑓(𝑥) = 3𝑥! − 8𝑥 − 2 5. 𝑓 𝑥 = 7𝑥!" − 7𝑥! − 5
Be able to tell (from a graph) if a function is 1-‐1. State if the given functions are inverses. 1. 𝑓 𝑥 = !
!!! , 𝑔 𝑥 = !
!− 3
2. ℎ 𝑥 = − 𝑥 + 2 ! ,𝑔 𝑥 = 𝑥 − 2! + 2 Find the inverse of each function. 1. 𝑓 𝑥 = 3 + !
!𝑥
2. ℎ 𝑥 = 𝑥 + 1 ! + 2 3. 𝑔 𝑥 = −1 − !
!𝑥
4. 𝑓 𝑥 = !!!!!!