# How do you solve #9 cos^3 x − 63 cos^2 x + cos x − 7 = 0 #?

##### 1 Answer

No solution.

#### Explanation:

**Pair #9cos^3x# and #cosx#. Pair #-63cos^2x# and #-7#.**

**Factor out each group.**

**Factor out #9cos^2x+1# from the entire expression.**

**For this to be true, #(9cos^2x+1)# or #(cosx-7)# must be equal to #0#.** However,

**However, this doesn't make any sense because any real number that is squared must be positive.**

Therefore, we can conclude that the equation has no solution.