Question

Which equation has x-intercepts located at (-1,0) and (-5,0)?

A. y=(x + 1)(x - 5)
B. y=(x + 1)(x + 5)
C. y=(x-1)(x - 5)
D. y=(x-1)(x + 5)

Answer 1

B. y = (x+1)(x+5)

Explanation:

If the x-intercepts are (-1,0) and (-5,0), then the solutions (also called zeros and x-intercepts) are

x = -1 and x = -5

This is a "working backwards" kind of problem. If you were solving the equation, right before the final step, x=-1 would have been:

x + 1 = 0

Right before x=-5

would have been,

x + 5 = 0.

These two: x+1 and x+5 are called the linear factors. You multiply them back together to find the equation.

y = (x+1)(x+5)