## Algebra and Trigonometry 10th Edition

$x^4-y^4$
We will use the result that $(a-b)(a+b)=a^2-b^2$ Hence, $(x+y)(x-y)(x^2+y^2)=(x^2-y^2)(x^2+y^2)$ (pairing the first two product terms and applying the result mentioned above) $(x^2-y^2)(x^2+y^2)=x^4-y^4$