Question

3arccos (2x+3)=5pi/2

Answer 1

$3arccos(2x+3)=\frac{5\pi }{2}\; \; \to \; \; arccos(2x+3)=\frac{5\pi }{6}\\\\cos(arccos(2x+3))=cos\frac{5\pi }{6}\\\\2x+3=cos(\pi -\frac{\pi}{6})\\\\2x+3=-cos\frac{\pi }{6}\\\\2x+3=-\frac{\sqrt3}{2}\\\\2x=-3-\frac{\sqrt3}{2}=-\frac{6+\sqrt3}{2}\\\\x=-\frac{6+\sqrt3}{4}$