Use Substitution to Determine Whether the Given X-Value Is a Solution

Multiple Choice

Use substitution to determine whether the given x-value is a solution of the equation.
Find All Solutions of a Trigonometric Equation
- $7 \cos x + 8 \sqrt { 2 } = 5 \cos x + 7 \sqrt { 2 }$

A) $x = \frac { 3 \pi } { 4 } + 2 n \pi$ or $x = \frac { 5 \pi } { 4 } + 2 n \pi$
B) $x = \frac { 3 \pi } { 4 } + n \pi$ or $x = \frac { 5 \pi } { 4 } + n \pi$
C) $x = \frac { \pi } { 4 } + 2 n \pi$ or $x = \frac { 7 \pi } { 4 } + 2 n \pi$
D) $x = \frac { \pi } { 4 } + n \pi$ or $x = \frac { 7 \pi } { 4 } + n \pi$