Solve the equation.
-$$x ^ { 4 } - 16 x ^ { 2 } - 225 = 0$$
A) $\{ - 5,5 , - 3,3 \}$
B) $\{ - 25,25 , - 9 i , 9 i \}$
C) $\{ - 5,5 , - 3 i , 3 i \}$
D) $\{ - 3,3 , - 5 i , 5 i \}$

Question

Quizplus · Accepted Answer

The equation can be rewritten as a quadratic in terms of $y = x^2$: $y^2 - 16y - 225 = 0$. Solving this quadratic gives $y = 25$ or $y = -9$. Thus, $x^2 = 25$ gives $x = \pm 5$ and $x^2 = -9$ gives $x = \pm 3i$.

Solve the Equation x4−16x2−225=0x ^ { 4 } - 16 x ^ { 2 } - 225 = 0x4−16x2−225=0

Solve the Equation $x ^ { 4 } - 16 x ^ { 2 } - 225 = 0$