Question

Using the completing-the-square method, rewrite f(x) = x2 4x − 1 in vertex form.

a. f(x) = (x +2)^2 + 1
b. f(x) = (x + 2^)2
c. f(x) = (x + 2^)2 + 4
d. f(x) = (x + 2)^2 − 5

Answer 1

Answer: D. f(x) = (x+2)^2 - 5

Very late, apologies! This answer is also for anyone who needs it in the future searching this question.

Proof of validity is shown below.

Answer 2

d) f(x)=(x+2)² -5
by the completion of the square