SOLUTION: solve using the 5 step problem solving process. Show all work. A number is 72 less than it's square. Find all such numbers.

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Question 300396: solve using the 5 step problem solving process. Show all work.
A number is 72 less than it's square. Find all such numbers.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A number is 72 less than it's square. Find all such numbers.
:
Let x = "a number"
:
x = x^2 - 72
A quadratic equation
0 = x^2 - x - 72
Factors to
(x-9)(x+8) = 0
x = +9
and
x = -8
:
Check both solution in original equation
x=9
9 = 9^2 - 72
9 = 81 - 72
x=-8
-8 = -8^2 - 72
-8 = +64 - 72