How do you solve 9x^2 - 7x = 12 using completing the square?

1 Answer
Gió
Jun 19, 2015

I found:
x_1=1/18(7+sqrt(481))
x_2=1/18(7-sqrt(481))

Explanation:

Let us do some manipulations:

9x^2-7x=12 add and subtract 49/36
9x^2-7x+49/36-49/36=12
9x^2-7x+49/36=12+49/36
(3x-7/6)^2=481/36 root square both sides:
3x-7/6=+-sqrt(481/36)=
x=1/3(7/6+-sqrt(481/36))
x_1=1/18(7+sqrt(481))
x_2=1/18(7-sqrt(481))

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