SOLUTION: complete the square x^2+20x=30 x= ? and ?

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Question 87888: complete the square
x^2+20x=30
x= ? and ?
Answer by rapaljer(4671) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E2%2B20x=30+

Assuming that the coefficient of x%5E2 is 1, you must take HALF of the x coefficient and SQUARE it, adding this quantity to each side of the equation as follows:
x%5E2+%2B20x+%2B_____=+30+%2B+____ Half of 20 is 10, and 10^2= 100!
x%5E2+%2B20x+%2B100=+30+%2B+100
%28x%2B10%29%5E2+=+130

Take the square root of each side:
+%28x%2B10%29+=+0%2B-+sqrt%28130%29+

Subtract 10 from each side:
x=+-10+%2B-+sqrt%28130%29+

R^2 Retired from SCC