### Home > CALC > Chapter 7 > Lesson 7.2.2 > Problem 7-70

7-70.

Once again, Greta is in a pickle! She is trying to solve the following equation and knows she can use

*u*-substitution to do it: Homework Help ✎3 tan

^{2}*x*− tan*x*− 10 = 0Greta thinks if she lets

*u*= tan*x*she can write the problem as a quadratic equation. Show Greta she is correct.Use your answer to part (a) to find the value(s) of

*x*.

3*u*^{2} − *u* − 10 = 0

Solve for *u*.

Then solve for *x*.

*x* = tan^{−1}(2) ≈ 1.107 + *πn*