7: \(=4\left[\left(8x-4\right)^2-\left(x+2\right)^2\right]\)
\(=4\left(8x-4-x-2\right)\left(8x-4+x+2\right)\)
\(=4\left(7x-6\right)\left(9x-2\right)\)
8: \(=\left(x-y\right)^2+4\left(x-y\right)=\left(x-y\right)\left(x-y+4\right)\)
9: \(=x^2-4x+4-y^2+2y-1\)
\(=\left(x-2\right)^2-\left(y-1\right)^2\)
\(=\left(x-2-y+1\right)\left(x-2+y-1\right)\)
\(=\left(x-y-1\right)\left(x+y-3\right)\)
10: \(=x^3\left(x-9\right)+x\left(x-9\right)=x\left(x-9\right)\left(x^2+1\right)\)
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