Question

Find the axis of the graph of the function.

f(x) = 4x2 + 8x + 7

x = 3

x = -1

x = -2

x = 2

Answer 1

"Completing the Square" Look it up. Read about it. Practice it. Get good at it.

f(x) = 4x^2 + 8x + 7

f(x) = (4x^2 + 8x) + 7

f(x) = 4(x^2 + 2x) + 7

f(x) = 4(x^2 + 2x + _______) + 7 - 4(______)

2/2 = 1
1^2 = 1

f(x) = 4(x^2 + 2x + 1) + 7 - 4(1)

f(x) = 4(x+1)^2 + 7 - 4

f(x) = 4(x+1)^2 + 3

It is now relatively obvious how to answer the question - IF you know how to see it in this form.