CPM Homework Help : PC3 Problem 9-131

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9-131.

Solve each of the following equations for all real $x$ .

$2\cos(3x) = 1$
Step 1 (a):
$\cos(3x)=\frac{1}{2}$
Step 2 (b):
Let $u = 3x$ . Then solve:
$\cos(u)=\frac{1}{2}$

$2\cos^2(x) + \cos(x) − 1 = 0$
Hint (b):
Let $u = \cos(x)$ . Then solve $2u^{2} + u − 1 = 0$ by factoring and using the Zero Product Property.

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