SOLUTION: x^2+7x=18

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Question 336178: x^2+7x=18
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

x%5E2%2B7x=18 Start with the given equation.


x%5E2%2B7x-18=0 Subtract 18 from both sides.


Notice that the quadratic x%5E2%2B7x-18 is in the form of Ax%5E2%2BBx%2BC where A=1, B=7, and C=-18


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-%287%29+%2B-+sqrt%28+%287%29%5E2-4%281%29%28-18%29+%29%29%2F%282%281%29%29 Plug in A=1, B=7, and C=-18


x+=+%28-7+%2B-+sqrt%28+49-4%281%29%28-18%29+%29%29%2F%282%281%29%29 Square 7 to get 49.


x+=+%28-7+%2B-+sqrt%28+49--72+%29%29%2F%282%281%29%29 Multiply 4%281%29%28-18%29 to get -72


x+=+%28-7+%2B-+sqrt%28+49%2B72+%29%29%2F%282%281%29%29 Rewrite sqrt%2849--72%29 as sqrt%2849%2B72%29


x+=+%28-7+%2B-+sqrt%28+121+%29%29%2F%282%281%29%29 Add 49 to 72 to get 121


x+=+%28-7+%2B-+sqrt%28+121+%29%29%2F%282%29 Multiply 2 and 1 to get 2.


x+=+%28-7+%2B-+11%29%2F%282%29 Take the square root of 121 to get 11.


x+=+%28-7+%2B+11%29%2F%282%29 or x+=+%28-7+-+11%29%2F%282%29 Break up the expression.


x+=+%284%29%2F%282%29 or x+=++%28-18%29%2F%282%29 Combine like terms.


x+=+2 or x+=+-9 Simplify.


So the solutions are x+=+2 or x+=+-9

If you need more help, email me at jim_thompson5910@hotmail.com

Also, feel free to check out my website.

Jim