Question

Use the process of completing the square and/or factoring to find the zeros and axis of symmetry for the graph of the function.

f(x) = x^2 - 14x - 72


A.

zeros: x = -4 and x = 18;

axis of symmetry: x = 7

B.

zeros: x = -18 and x = 4;

axis of symmetry: x = -7

C.

zeros: x = -9 and x = -8;

axis of symmetry: x = -7

D.

zeros: x = 9 and x = 8;

axis of symmetry: x = 7

EDIT: The answer is here.

The axis of symmetry is 7.
The roots were 18 & -4

Answer 1

I believe it is D .

Answer 2

A)

zeros: x = -4 and x = 18;

axis of symmetry: x = 7

Explanation:

Given the equation of function

f(x) = x² - 14x - 72

here a = 2

b = -14

c = -72

by using quadratic equation

x = ( -b ± √b² - 4ac ) / 2a

x1 = 14 + √14² + 4(1)(72) / 2

= 18

and

x2 = 14 - √14² + 4(1)(72) / 2

= - 4

For symmetry of axis

It is a vertical line with the equation of x = -b/2a

x = -(-14)/2(1)

x = 7