# Math Help - Ellipse

1. ## Ellipse

[LEFT]Determine the length of the ray focal of the point $M(3,\frac{7}{4})$who is on the ellipse $7x^2+16y^2=112$

Answer:
$\frac{25}{4}$ and $\frac{7}{4}$

2. Originally Posted by Apprentice123
[LEFT]Determine the length of the ray focal of the point $M(3,\frac{7}{4})$who is on the ellipse $7x^2+16y^2=112$

Answer:
$\frac{25}{4}$ and $\frac{7}{4}$
That ellipse can also be written (divide both sides by 112) $\frac{x^2}{112}+ \frac{y^2}{7}= \frac{x^2}{(4\sqrt{7})^2}+ \frac{y^2}{(\sqrt{7})^2}= 1$.

That has semi-axes of length $\sqrt{7}$ and $4\sqrt{7}$. Can you calculate the coordinates of the foci from that? Then it should be easy to find the distance from that point to each point.