Solve for all solutions

Question

Solve 8cos^2(x)+2cos(x)-3=0 for all solutions 0<=x<2pi

x=____________

Answers accurate to 2 decimal places

Answer 1

Let y = cos(x). Then you can think of it as a quadratic equation 8y^2 + 2y - 3 = 0. Find the possibilities for y and then find the possibilities for x.