## Intermediate Algebra (6th Edition)

$x^{3a}+5x^{2a}-3x^a-15$
Using $(a+b)(c+d)=ac+ad+bc+bd$ or the FOIL Method and using the laws of exponents, the given expression, $(x^a+5)(x^{2a}-3)$, is equivalent to \begin{array}{l}\require{cancel} x^{a+2a}-3x^a+5x^{2a}-15 \\\\= x^{3a}+5x^{2a}-3x^a-15 .\end{array}