Quadratic Equation and Inequalities

Let $\alpha$ and $\beta$ be two real roots of the equation (k + 1)tan²x - $\sqrt 2$ . $\lambda$tanx = (1 - k), where k($\ne$ - 1) and $\lambda$ are real numbers. if tan² ($\alpha$ + $\beta$) = 50, then a value of $\lambda$ is: