Question

One factor of $x^4+x^2$ - 20 is $x^2$ +5, the other is

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

Answer 1

The correct option is C

$x^2$ - 4

$x^2$ + 5 is a factor of f(x) = $x^4+x^2-20$

Now dividing f(x) by $x^2+5$, we get

$f\left(x\right)=(x^2+5)(x^2$-4)

$\therefore$ Other factor is $x^2-4$