Writing Function Rules Teacher Twins©2014

Warm Up Graph each function. 1. y = 4x + 5 2. y = -3x + 1

Writing Functions Rules

Ex 1: Write a function rule for the given table of values. Think how does -1 become -2? Multiply by 2 or add -1. Try both to see which one works. -1 x 2 = -2 -1 + -1 = -2 0 x 2 = 0 0 + -1 = -1 1 x 2 = 2 Does not 2 x 2 = 4 work. works Function Rule y = 2x

Ex 2: Write a function rule for the given table of values. How does -2 become -10? Guess and check functions until you find the correct one. X 5 does not work + -8 does not work Try multiplying then adding a number or subtracting a number. X3 – 4 -2(3) – 4 = -10 0(3) – 4 = -4 2(3) – 4 = 2 4(3) – 4 = 8 Works y = 3x - 4

Practice Write the function rule. 1. 2. y = - 3x y = x + 6

Closure How many rules can you create that make -2 turn into -6?