SOLUTION: Quadratic Equations Solve by factoring: x2 – 9x = -20 So lost

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Question 28480: Quadratic Equations
Solve by factoring:
x2 – 9x = -20
So lost
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Solve by factoring:
x%5E2-9x+=+-20 First, add 20 to both sides of the equation.
x%5E2-9x%2B20+=+0 Now factor the left side.
Factoring: The two factors will have the form%28x%2Ba%29%28x%2Bb%29 where: a+b = -9
and a X b = 20
Try these: a = -4 and b = -5
a+b = (-4)+(-5) = -9
a X b = (-4)(-5) = 20 So these will work.
The factors are:
(x-4)(x-5), so we have:
(x-4)(x-5) = 0 Apply the zero products principle.
x-4 = 0 and/or x-5 = 0
If x-4 = 0, then x = 4
If x-5 = 0, then x = 5
The roots are:
x = 4
x = 5