Question 207259
x^2 -20x =0
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x^2 -20x +(20/2)^2 = (20/2)^2
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x^2 -20x +100 = 100
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(x-10)^2 =100
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take  sqrt  of  both  sides
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+/- (x-10) = +/- 10
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(x-10) =10,,,x=20,,check,,(20)^2 -20(20)=0,,400-400=0,,ok
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(x-10)= -10,,,x=0,,check,,(0)^2 -20(0)=0,,,ok
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-x+10=10,,x=0,,,check,,ok
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-x+10=-10,,x=20,,check,,ok
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Therefore,,,x=0,20