Solve.
-$$( 2 x - 4 ) ^ { 2 } - 4 ( 2 x - 4 ) - 21 = 0$$
A) $\left\{ \frac { 1 } { 2 } , \frac { 11 } { 2 } \right\}$
B) $\left\{ \frac { 7 } { 2 } , - \frac { 3 } { 2 } \right\}$
C) $\left\{ - \frac { 1 } { 2 } , - \frac { 11 } { 2 } \right\}$
D) $\left\{ - \frac { 7 } { 4 } , \frac { 3 } { 2 } \right\}$

Question

Quizplus · Accepted Answer

Let $y = 2x - 4$. The equation becomes $y^2 - 4y - 21 = 0$. Factoring or using the quadratic formula gives $y = 7$ or $y = -3$. Substituting back for $x$, we get $x = \frac{1}{2}$ or $x = \frac{11}{2}$.

Solve - (2x−4)2−4(2x−4)−21=0( 2 x - 4 ) ^ { 2 } - 4 ( 2 x - 4 ) - 21 = 0(2x−4)2−4(2x−4)−21=0

Solve
- $( 2 x - 4 ) ^ { 2 } - 4 ( 2 x - 4 ) - 21 = 0$