SOLUTION: Complete the square 2x^2-3x-8

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Question 778862: Complete the square
2x^2-3x-8
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+2x%5E2+-+3x+-+8+=+0+
+2x%5E2+-+3x+=+8+
+x%5E2+-+%283%2F2%29%2Ax+=+4+
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Take 1/2 of the coefficient of the x-term,
square it, and add it to both sides
+x%5E2+-+%283%2F2%29%2Ax+%2B+%283%2F4%29%5E2+=+4+%2B+%283%2F4%29%5E2+
+x%5E2+-+%283%2F2%29%2Ax+%2B+9%2F16+=+64%2F16+%2B+9%2F16++
+%28+x+-++3%2F4+%29%5E2+=+73%2F16+
Take the square root of both sides
+x+-+3%2F4+=+sqrt%2873%29%2F4+
+x++=+%28+3+%2B+sqrt%2873+%29%29+%2F+4+
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Now take the (-) square root of the right side
+x+-+3%2F4+=+-+sqrt%2873+%29+%2F+4++
+x+=+%28+3+-+sqrt%2873%29%29+%2F+4+
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check:



+x%5E2+-+%283%2F2%29%2Ax++-+4+=+0+
+2x%5E2+-+3x+-+8+=+0+
OK