SOLUTION: x2 -6x-7=0

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Question 180789: x2 -6x-7=0
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

x%5E2-6x-7=0 Start with the given equation.


Notice we have a quadratic equation in the form of ax%5E2%2Bbx%2Bc where a=1, b=-6, 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-%28-6%29+%2B-+sqrt%28+%28-6%29%5E2-4%281%29%28-7%29+%29%29%2F%282%281%29%29 Plug in a=1, b=-6, and c=-7


x+=+%286+%2B-+sqrt%28+%28-6%29%5E2-4%281%29%28-7%29+%29%29%2F%282%281%29%29 Negate -6 to get 6.


x+=+%286+%2B-+sqrt%28+36-4%281%29%28-7%29+%29%29%2F%282%281%29%29 Square -6 to get 36.


x+=+%286+%2B-+sqrt%28+36--28+%29%29%2F%282%281%29%29 Multiply 4%281%29%28-7%29 to get -28


x+=+%286+%2B-+sqrt%28+36%2B28+%29%29%2F%282%281%29%29 Rewrite sqrt%2836--28%29 as sqrt%2836%2B28%29


x+=+%286+%2B-+sqrt%28+64+%29%29%2F%282%281%29%29 Add 36 to 28 to get 64


x+=+%286+%2B-+sqrt%28+64+%29%29%2F%282%29 Multiply 2 and 1 to get 2.


x+=+%286+%2B-+8%29%2F%282%29 Take the square root of 64 to get 8.


x+=+%286+%2B+8%29%2F%282%29 or x+=+%286+-+8%29%2F%282%29 Break up the expression.


x+=+%2814%29%2F%282%29 or x+=++%28-2%29%2F%282%29 Combine like terms.


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


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