Answer
$x^3-x^2-x-15$
Work Step by Step
$(x-3)(x^2+2x+5)=\\=x(x^2+2x+5)-3(x^2+2x+5)\\=(x^3+2x^2+5x)-3x^2-6x-15\\=x^3-x^2-x-15$
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