# How to find critical points and the highest point on the graph of #4x^2 + 4xy+7y^2=15#?

##### 1 Answer

Find

#### Explanation:

so we have (in the original equation):

Solve for

Now substitute in the original equation and solve for

For

and for

Obviously the high point is at the positive

(Really, we also have critical points when

Here is the graph:

graph{4x^2 + 4xy+7y^2=15 [-4.385, 4.384, -2.19, 2.195]}