Question 252486
Hint: Recall that *[Tex \LARGE sin^2(x)+cos^2(x)=1]. 



So this means that *[Tex \LARGE sin^2(x)=1-cos^2(x)]. 



So plug in *[Tex \LARGE sin^2(x)=1-cos^2(x)] to get *[Tex \LARGE 2\left(1-cos^2(x)\right)+3cos(x)=3]. 



Now let *[Tex \LARGE z=cos(x)] and plug that in to get:  *[Tex \LARGE 2(1-z^2)+3z=3]. 



At this point, we have a quadratic which can be solved by the quadratic formula. You'll get solutions in terms of 'z', so you'll need to remember to use *[Tex \LARGE z=cos(x)] to find the solutions in terms of 'x'. Let me know if you still need help.