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

Question

Christine Yu

Mathematics

8 May, 16:04

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

+4

Answers (2)

Know the Answer?

Shawn Chang · Answer 1

I believe it is D.

Tomas Huber · Answer 2

A)

zeros: x = - 4 and x = 18;

axis of symmetry: x = 7

Step-by-step 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