SOLUTION: x^2+8x-20=0

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Question 560575: x^2+8x-20=0
Answer by jim_thompson5910(35256) About Me  (Show Source):
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x%5E2%2B8x-20=0 Start with the given equation.


Notice that the quadratic x%5E2%2B8x-20 is in the form of Ax%5E2%2BBx%2BC where A=1, B=8, and C=-20


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%28-20%29+%29%29%2F%282%281%29%29 Plug in A=1, B=8, and C=-20


x+=+%28-8+%2B-+sqrt%28+64-4%281%29%28-20%29+%29%29%2F%282%281%29%29 Square 8 to get 64.


x+=+%28-8+%2B-+sqrt%28+64--80+%29%29%2F%282%281%29%29 Multiply 4%281%29%28-20%29 to get -80


x+=+%28-8+%2B-+sqrt%28+64%2B80+%29%29%2F%282%281%29%29 Rewrite sqrt%2864--80%29 as sqrt%2864%2B80%29


x+=+%28-8+%2B-+sqrt%28+144+%29%29%2F%282%281%29%29 Add 64 to 80 to get 144


x+=+%28-8+%2B-+sqrt%28+144+%29%29%2F%282%29 Multiply 2 and 1 to get 2.


x+=+%28-8+%2B-+12%29%2F%282%29 Take the square root of 144 to get 12.


x+=+%28-8+%2B+12%29%2F%282%29 or x+=+%28-8+-+12%29%2F%282%29 Break up the expression.


x+=+%284%29%2F%282%29 or x+=++%28-20%29%2F%282%29 Combine like terms.


x+=+2 or x+=+-10 Simplify.


So the solutions are x+=+2 or x+=+-10
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