1) Divide through by 2, square both sides, and solve the linear equation.
2) Square both sides. Then solve the resulting quadratic equation.
3) If this is an equation, there's a typo, because there is no "equals" sign. If this is an expression, then follow the procedure they taught you for rationalizing denominators (which will, as a side effect in this case, give you the common denominator).
If you get stuck, please reply showing how far you have gotten. Thank you.