Which functions have an axis of symmetry of x = –2? Check all that apply.

f(x) = x2 + 4x + 3

f(x) = x2 – 4x – 5

f(x) = x2 + 6x + 2

f(x) = –2x2 – 8x + 1

f(x) = –2x2 + 8x – 2

Verified Answer :

the answer is the first one and the fourth one

Answer : \(Answer :f(x) = x^2 + 4x + 3 \ and \ f(x) = -2x^2 - 8x + 1\)

Given: axis of symmetry of x = –2

To find axis of symmetry we use formula \(x =\frac{-b}{2a}\)

We check which equation has axis of symmetry x= -2

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

a=1 , b=4 so axis of symmetry \(x =\frac{-4}{2*1} = -2\)

(2) \(f(x) = x^2 - 4x - 5\)

a=1 , b=-4 so axis of symmetry \(x =\frac{-(-4)}{2*1} = 2\)

(3) \(f(x) = x^2 + 6x + 2\)

a=1 , b=6 so axis of symmetry \(x =\frac{-6}{2*1} = -3\)

(4) \(f(x) = -2x^2 - 8x + 1\)

a=-2 , b=-8 so axis of symmetry \(x =\frac{-(-8)}{2*(-2)} = -2\)

(5) \(f(x) = -2x^2 + 8x - 2\)

a=-2 , b=8 so axis of symmetry \(x =\frac{-(8)}{2*(-2)} = 2\)

So \(f(x) = x^2 + 4x + 3\) and \(f(x) = -2x^2 - 8x + 1\) has axis of symmetry x=-2