SOLUTION: Use the quadratic formula to solve: x^2+8x+7=0

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Question 178397This question is from textbook
: Use the quadratic formula to solve: x^2+8x+7=0 This question is from textbook

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

x%5E2%2B8x%2B7=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=7


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%287%29+%29%29%2F%282%281%29%29 Plug in a=1, b=8, and c=7


x+=+%28-8+%2B-+sqrt%28+64-4%281%29%287%29+%29%29%2F%282%281%29%29 Square 8 to get 64.


x+=+%28-8+%2B-+sqrt%28+64-28+%29%29%2F%282%281%29%29 Multiply 4%281%29%287%29 to get 28


x+=+%28-8+%2B-+sqrt%28+36+%29%29%2F%282%281%29%29 Subtract 28 from 64 to get 36


x+=+%28-8+%2B-+sqrt%28+36+%29%29%2F%282%29 Multiply 2 and 1 to get 2.


x+=+%28-8+%2B-+6%29%2F%282%29 Take the square root of 36 to get 6.


x+=+%28-8+%2B+6%29%2F%282%29 or x+=+%28-8+-+6%29%2F%282%29 Break up the expression.


x+=+%28-2%29%2F%282%29 or x+=++%28-14%29%2F%282%29 Combine like terms.


x+=+-1 or x+=+-7 Simplify.


So the answers are x+=+-1 or x+=+-7