Question

(х-5)(х-5)-5=4(4-х)+4=?
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Answer 1

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$\displaystyle \bf\Big(x-5\Big)\Big(x-5\Big)-5=4\Big(4-x\Big)+4\\\\\\\Big(x-5\Big)^2=16-4x+4\\\\\\x^2-10x+20=-4x+20\\\\\\x^2-10x+4x=20-20\\\\\\x^2-6x=0$

$\displaystyle \bf D=b^2-4ac=\Big(-6\Big)^2-4\cdot 1\cdot 0=36\\\\\sqrt{D}=\sqrt{36} =6$

$\boxed{ \Big \displaystyle \bf X_1=\frac{-\left(-6\right)+6}{2\cdot \:1}=\frac{12}{2}=6 \\\\\\\\}$

$\boxed{\Big \displaystyle \bf X_2=\frac{-\left(-6\right)-6}{2\cdot \:1}=0}$