How will u find out that if the point $\displaystyle (\alpha, \beta)$ is outside, on or inside the ellipse $\displaystyle \frac{x^2}{a^2} + \frac{y^2}{b^2} = 1 $?

Hence show that the triangle whose verities are (1,2), (3,-11) and (-2,1) lies wholly inside the ellipse $\displaystyle x^2 + 2y^2 = 13.$