SOLUTION: verify that x=-2 is solution of equation 3(2x+3)

SOLUTION: verify that x=-2 is solution of equation 3(2x+3) - x*x = 2x + 7

Question 200741: verify that x=-2 is solution of equation 3(2x+3) - x*x = 2x + 7
Answer by RAY100(1637) (Show Source): You can put this solution on YOUR website!
Normal method to verify is to substitute answer into eqn
.
3(2x+3) -x*x = 2x +7
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3 [ 2(-2) +3] -(-2)*(-2) = 2(-2) +7
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3[ -1] -4 = -4+7
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-3-4=3
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-7 = 3,,,,not true, not verified
.
lets just solve eqn
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3(2x+3) -x*x =2x +7
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6x +9 -x^2 = 2x+7
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0 = x^2 -4x -2
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use quadratic eqn to solve,,,,,a=1,,,,b=-4,,,,,c=-2
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x = [ -(-4) +/- sqrt{ (-4)^2 -4 (1) (-2)} ] / 2(1)
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x=[ 4 +/- sq rt { 16 +8} ] /2
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x= [ 4 +/- sqrt 24]/2
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x= [ 4 +/- 4.9] /2
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x= +4.4, -.45
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to verify these
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x^2 -4x -2 =0
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(4.4)^2 -4(4.4) -2 =0,,,,,ok
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(.45)^2 -4(.45) -2 =0,,,,,ok
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