Answer
$x(x+1)$
Work Step by Step
$(x+1)^{3}x-2(x+1)^{2}x^{2}+x^{3}(x+1)=x(x+1)[(x+1)^{2}-2(x+1)x+x^{2}]=x(x+1)[(x+1)-x]^{2}=x(x+1)[x-x+1]^{2}
=x(x+1)(1)^{2}=x(x+1)$
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