# Inspired by Mridul Jain

Geometry Level 5

$\large x_n=a \sin n\theta+b\cos n\theta$

Find $$x_7$$ if the numbers $$a,$$ $$b$$ and $$\theta$$ satisfy the following equations: $$x_1=15,$$ $$x_2=3,$$ and $$x_3=-12.$$

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