SOLUTION: Solve by using the quadratic formula. Show complete solutions. 2x^2 + 9x - 7 = 0

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Question 325297: Solve by using the quadratic formula. Show complete solutions.
2x^2 + 9x - 7 = 0
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
2x%5E2%2B9x-7=0 Start with the given equation.


Notice that the quadratic 2x%5E2%2B9x-7 is in the form of Ax%5E2%2BBx%2BC where A=2, B=9, 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-%289%29+%2B-+sqrt%28+%289%29%5E2-4%282%29%28-7%29+%29%29%2F%282%282%29%29 Plug in A=2, B=9, and C=-7


x+=+%28-9+%2B-+sqrt%28+81-4%282%29%28-7%29+%29%29%2F%282%282%29%29 Square 9 to get 81.


x+=+%28-9+%2B-+sqrt%28+81--56+%29%29%2F%282%282%29%29 Multiply 4%282%29%28-7%29 to get -56


x+=+%28-9+%2B-+sqrt%28+81%2B56+%29%29%2F%282%282%29%29 Rewrite sqrt%2881--56%29 as sqrt%2881%2B56%29


x+=+%28-9+%2B-+sqrt%28+137+%29%29%2F%282%282%29%29 Add 81 to 56 to get 137


x+=+%28-9+%2B-+sqrt%28+137+%29%29%2F%284%29 Multiply 2 and 2 to get 4.


x+=+%28-9%2Bsqrt%28137%29%29%2F%284%29 or x+=+%28-9-sqrt%28137%29%29%2F%284%29 Break up the expression.


So the solutions are x+=+%28-9%2Bsqrt%28137%29%29%2F%284%29 or x+=+%28-9-sqrt%28137%29%29%2F%284%29