$\text{a)}$  

$W\left(x\right)=-x^2\left(x+1\right)+49\left(x+1\right)$  

$W\left(x\right)=\left(x+1\right)\cdot \left(-x^2+49\right)$     

$W\left(x\right)=\left(x+1\right)\cdot \left(-1\right)\left(x^2-49\right)$  

$W\left(x\right)=-1\left(x+1\right)\left(x-7\right)\left(x+7\right)$  

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$\text{b)}$  

$W\left(x\right)=2x\left(x^2-9\right)+5\left(9-x^2\right)$  

$W\left(x\right)=2x\left(x^2-9\right)+5\left(-1\left(-9+x^2\right)\right)$  

$W\left(x\right)=2x\left(x^2-9\right)-5\left(-9+x^2\right)$  

$W\left(x\right)=\left(x^2-9\right)\left(2x-5\right)$