Question

The expression $a^4-2a^3-4a+8$ can be factorise as

• A. $(a^3+4)(a-2)$
• B. $(a^3-4)(a+2)$
• C. $(a^3+4)(a+2)$
• D. $(a^3-4)(a-2)$

Answer 1

The correct option is D $(a^3-4)(a-2)$

The given expression can be written as
$a^4-2a^3-4a+8$
= $a^3(a-2)-4(a-2)$ [Taking $a^3$ common]
= $(a^3-4)(a-2)$ [Taking $a-2$ common]

Hence, it can be factorise as
$(a^3-4)(a-2)$