Question

The continued product of $(x+3)(x-3)(x^2+9)$ is

• A. $-x^4+81$
• B. $x^2-81$
• C. $x^4-18$
• D. $x^4-81$

Answer 1

The correct option is D $x^4-81$

Given equation is: $(x+3)(x-3)(x^2+9)$

Using the identity $(a+b)(a-b)=a^2-b^2$
$\therefore (x+3)(x-3)(x^2+9)$ =$(x^2-9)(x^2+9)$
=$(x^2{)}^2-9^2$
= $x^4-81$