SOLUTION: x^2+10x+10=0 I know the answer is neg 5 plus or minus the square root of 15 but why?

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Question 303014: x^2+10x+10=0
I know the answer is neg 5 plus or minus the square root of 15 but why?
Answer by TX911(36) About Me  (Show Source):
You can put this solution on YOUR website!
The quadratic formula reads : x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
So it would be x=%28-10%2B-+sqrt%2810%5E2-4%2A1%2A10%29%29%2F%282%2Aa%29
so basically -10 +- sqrt of 100-40 which is 60/ over 2 because your leading coefficient of x^2 is actually a 1. Factor out your square root of 60 which would be 2 square root 15. So now we have -10+- %28+2sqrt%2815%29%29%2F%282%29 Divide everything on the top by your denominator of 2 to get %28-5+%2B-+sqrt+%2815%29%29
The denominator of course cancels. So that's what you're left with