Question

Consider the quadratic function that has x-intercepts of–1 and –7 and passes through the point (-2,-20). What is the

value of a in the factored form of this function?
1, 2,3,4?

Answer 1

Short Answer: a = 4
Remark: How did this escape deletion?

Step One
Set up the factored equation with a constant to solve the constant effecting all parts of the quadratic.

The roots are -7 and -1
The factors are (x + 7)(x + 1)

Step two
Write the equation
y = a*(x +7)(x + 1)

Step three
Solve for a. Use (-2,-20)
y = -20
x = -2

-20 = a(-2 + 7)(-2 + 1)
-20 = a (5)(-1)
-20 = -5a Divide by -5
a = -20/-5
a = 4

Step 4.
Write the equation with a
y = 4(x + 7)(x + 1)

a = 4