SOLUTION: 4x^2+x-20=0

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Question 926130: 4x^2+x-20=0
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

4x%5E2%2Bx-20=0 Start with the given equation.


Notice that the quadratic 4x%5E2%2Bx-20 is in the form of Ax%5E2%2BBx%2BC where A=4, B=1, 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-%281%29+%2B-+sqrt%28+%281%29%5E2-4%284%29%28-20%29+%29%29%2F%282%284%29%29 Plug in A=4, B=1, and C=-20


x+=+%28-1+%2B-+sqrt%28+1-4%284%29%28-20%29+%29%29%2F%282%284%29%29 Square 1 to get 1.


x+=+%28-1+%2B-+sqrt%28+1--320+%29%29%2F%282%284%29%29 Multiply 4%284%29%28-20%29 to get -320


x+=+%28-1+%2B-+sqrt%28+1%2B320+%29%29%2F%282%284%29%29 Rewrite sqrt%281--320%29 as sqrt%281%2B320%29


x+=+%28-1+%2B-+sqrt%28+321+%29%29%2F%282%284%29%29 Add 1 to 320 to get 321


x+=+%28-1+%2B-+sqrt%28+321+%29%29%2F%288%29 Multiply 2 and 4 to get 8.


x+=+%28-1%2Bsqrt%28321%29%29%2F%288%29 or x+=+%28-1-sqrt%28321%29%29%2F%288%29 Break up the expression.


So the exact solutions are x+=+%28-1%2Bsqrt%28321%29%29%2F%288%29 or x+=+%28-1-sqrt%28321%29%29%2F%288%29
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