SOLUTION: Use factoring to solve the quadratic equation, check by substitution or by using a graphing utility and identifying x-intercepts. x^2-x-72=0

Question 271070: Use factoring to solve the quadratic equation, check by substitution or by using a graphing utility and identifying x-intercepts.
x^2-x-72=0
Answer by LarissaRichardson(34) (Show Source): You can put this solution on YOUR website!
x^2-x-72=0
Reverse Foil
A.What multiplied together will give you x^2?
Answer x times x
B. What multiplied together will give you negative 72 and added will give you negative 1?
Answer -9 times 8
Written as:
(x-9)(x+8)
And when you foil this you get your original problem of x^2-x-72
Now set both equal to zero
x-9=0
x=0+9
x=9
x+8=0
x=0-8
x=-8
Check both answers in original equation for correct answer.
9^2-9-72=0?
81-9-72=0?
72-72=0?Yes
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