\textbf{114-} The sum of the solutions of the trigonometric equation $\sqrt{7}\sin x + \sqrt{3}\cos x = \sqrt{7}$ on the interval $[-\pi, 2\pi]$ is which of the following?
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(1) $\dfrac{\pi}{2}$ \hfill (2) $\dfrac{7\pi}{3}$ \hfill (3) $\dfrac{9\pi}{4}$ \hfill (4) $\dfrac{11\pi}{6}$
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