Let f(x)=6x3+13x2−4x−15f(x) = 6x^3 + 13x^2 - 4x - 15f(x)=6x3+13x2−4x−15.
Use the factor theorem to show that (2x+3)(2x + 3)(2x+3) is a factor of f(x)f(x)f(x).
Hence, using algebra, write f(x)f(x)f(x) as a product of three linear factors.
Solve, for π2<θ<π\frac{\pi}{2} < \theta < \pi2π<θ<π, the equation
6tan3θ+13tan2θ−4tanθ−15=0 6\tan^3 \theta + 13\tan^2 \theta - 4\tan \theta - 15 = 0 6tan3θ+13tan2θ−4tanθ−15=0giving your answers to 3 significant figures.