SOLUTION: Solve. x2 + 8x + 15 = 0

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Solve. x2 + 8x + 15 = 0       Log On


   

Question 366180: Solve. x2 + 8x + 15 = 0


Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

x%5E2%2B8x%2B15=0 Start with the given equation.


Notice we have a quadratic equation in the form of ax%5E2%2Bbx%2Bc where a=1, b=8, and c=15


Let's use the quadratic formula to solve for x


x+=+%28-b+%2B-+sqrt%28+b%5E2-4ac+%29%29%2F%282a%29 Start with the quadratic formula


x+=+%28-%288%29+%2B-+sqrt%28+%288%29%5E2-4%281%29%2815%29+%29%29%2F%282%281%29%29 Plug in a=1, b=8, and c=15


x+=+%28-8+%2B-+sqrt%28+64-4%281%29%2815%29+%29%29%2F%282%281%29%29 Square 8 to get 64.


x+=+%28-8+%2B-+sqrt%28+64-60+%29%29%2F%282%281%29%29 Multiply 4%281%29%2815%29 to get 60


x+=+%28-8+%2B-+sqrt%28+4+%29%29%2F%282%281%29%29 Subtract 60 from 64 to get 4


x+=+%28-8+%2B-+sqrt%28+4+%29%29%2F%282%29 Multiply 2 and 1 to get 2.


x+=+%28-8+%2B-+2%29%2F%282%29 Take the square root of 4 to get 2.


x+=+%28-8+%2B+2%29%2F%282%29 or x+=+%28-8+-+2%29%2F%282%29 Break up the expression.


x+=+%28-6%29%2F%282%29 or x+=++%28-10%29%2F%282%29 Combine like terms.


x+=+-3 or x+=+-5 Simplify.


So the answers are x+=+-3 or x+=+-5