SOLUTION: Please help! Solve by using quadratic formula {{{ ax^2+bx+c=0 }}}. {{{ 4x^2+x-1=0 }}}

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Question 625897: Please help! Solve by using quadratic formula +ax%5E2%2Bbx%2Bc=0+.
+4x%5E2%2Bx-1=0+
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

4x%5E2%2Bx-1=0 Start with the given equation.


Notice that the quadratic 4x%5E2%2Bx-1 is in the form of Ax%5E2%2BBx%2BC where A=4, B=1, and C=-1


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-%281%29+%2B-+sqrt%28+%281%29%5E2-4%284%29%28-1%29+%29%29%2F%282%284%29%29 Plug in A=4, B=1, and C=-1


x+=+%28-1+%2B-+sqrt%28+1-4%284%29%28-1%29+%29%29%2F%282%284%29%29 Square 1 to get 1.


x+=+%28-1+%2B-+sqrt%28+1--16+%29%29%2F%282%284%29%29 Multiply 4%284%29%28-1%29 to get -16


x+=+%28-1+%2B-+sqrt%28+1%2B16+%29%29%2F%282%284%29%29 Rewrite sqrt%281--16%29 as sqrt%281%2B16%29


x+=+%28-1+%2B-+sqrt%28+17+%29%29%2F%282%284%29%29 Add 1 to 16 to get 17


x+=+%28-1+%2B-+sqrt%28+17+%29%29%2F%288%29 Multiply 2 and 4 to get 8.


x+=+%28-1%2Bsqrt%2817%29%29%2F%288%29 or x+=+%28-1-sqrt%2817%29%29%2F%288%29 Break up the expression.


So the solutions are x+=+%28-1%2Bsqrt%2817%29%29%2F%288%29 or x+=+%28-1-sqrt%2817%29%29%2F%288%29
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