SOLUTION: 4x^2+8x+5=0

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Question 600338: 4x^2+8x+5=0
Found 2 solutions by jim_thompson5910, stanbon:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

4x%5E2%2B8x%2B5=0 Start with the given equation.


Notice we have a quadratic equation in the form of ax%5E2%2Bbx%2Bc where a=4, b=8, and c=5


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-%288%29+%2B-+sqrt%28+%288%29%5E2-4%284%29%285%29+%29%29%2F%282%284%29%29 Plug in a=4, b=8, and c=5


x+=+%28-8+%2B-+sqrt%28+64-4%284%29%285%29+%29%29%2F%282%284%29%29 Square 8 to get 64.


x+=+%28-8+%2B-+sqrt%28+64-80+%29%29%2F%282%284%29%29 Multiply 4%284%29%285%29 to get 80


x+=+%28-8+%2B-+sqrt%28+-16+%29%29%2F%282%284%29%29 Subtract 80 from 64 to get -16


x+=+%28-8+%2B-+sqrt%28+-16+%29%29%2F%288%29 Multiply 2 and 4 to get 8.


x+=+%28-8+%2B-+4%2Ai%29%2F%288%29 Take the square root of -16 to get 4%2Ai.


x+=+%28-8+%2B+4%2Ai%29%2F%288%29 or x+=+%28-8+-+4%2Ai%29%2F%288%29 Break up the expression.


x+=+%28-2+%2B+i%29%2F2 or x+=++%28-2+-+i%29%2F2 Reduce.


So the answers are x+=+%28-2+%2B+i%29%2F2 or x+=++%28-2+-+i%29%2F2


Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
4x^2+8x+5=0
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x = [-8 +- sqrt(64-4*4*5)]/8
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x = [-8 +- sqrt(-16)]/8
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x = [-8 +- 4i]/8
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x = -1+(i/2) or x = -1-(i/2)
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Cheers,
Stan H.
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