(x+2) is a factor of

From the factor theorem, we have

(x + 2) is the factor of f(x) if (f-2) = 0

Here, we have

f(-2) = (-2)⁴ – (-2)² – 12

= 16 – 4 – 12

= 16 – 16

= 0

Therefore,

(x + 2) is a factor of (x⁴ – x² – 12)