SOLUTION: when twice a number is subtracted from the square of the number, the result is 99. determine the number

Question 839719: when twice a number is subtracted from the square of the number, the result is 99. determine the number
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
your equation is x^2 - 2x = 99
subtract 99 from both sides of this equation to get:
x^2 - 2x - 99 = 0
factor to get:
(x - 11) * (x + 9) = 0
solve for x to get:
x = 11 or x = -9

since there are no restrictions on the sign of the answer, both answers are good.
the graph of the equation is shown below:

the solution to the equation are the roots of the equation which is where the graph of the equation crosses the x-axis.

your original equation is x^2 - 2x = 99
when x = 11, this becomes 121 - 22 = 99 which becomes 99 = 99.
when x = -9, this becomes 81 + 18 = 99 which becomes 99 = 99.
both solutions are good.

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