Algebra 1 problem help:Completing the sqaure?
Solve x^2+7x=120 by completing the square, please show your work?
Thank you!
Solve x^2+7x=120 by completing the square, please show your work?
Thank you!
sepia
Favorite Answer
x^2 + 7x = 120
(x + 7/2)^2 - 529/4 = 0
(x + 7/2)^2 = 529/4
x + 3.5 = +/- 11.5
Solutions:
x = -15
x = 8
Sqdancefan
Half the x-coefficient is 3.5, so we add the square of that to both sides. Then rearrange.
.. x^2 +7x +3.5^2 = 120 +3.5^2
.. (x +3.5)^2 = 132.25
.. x +3.5 = ±11.5 . . . . . . . . take the square root of both sides
.. x = -3.5 ± 11.5 . . . . . . . . add -3.5
.. x = {-15, -8}