\(4-3x-x^2=-\left(x^2+3x-4\right)\)
\(=-\left(x^2+4x-x-4\right)\)
\(=-\left[\left(x^2-x\right)+\left(4x-4\right)\right]\)
\(=-\left[x\left(x-1\right)+4\left(x-1\right)\right]\)
\(=-\left(x+4\right)\left(x-1\right)\)
\(8-x-7x^2=-\left(7x^2+x-8\right)\)
\(=-\left(7x^2-7x+8x-8\right)\)
\(=-\left[\left(7x^2-7x\right)+\left(8x-8\right)\right]\)
\(=-\left[7x\left(x-1\right)+8\left(x-1\right)\right]\)
\(=-\left(7x+8\right)\left(x-1\right)\)
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