# How do I convert the equation #-9x^2 +4y^2 +72x-16y =164# to standard form?

##### 1 Answer

We need to complete the square for the

First, reorder the terms

**Factor out a #-9# from the first 2 terms.**

*Remember to change the signs.

**Factor out a #4# from the last 2 terms.**

**Work with the #x# term.**

Remember that we factor out

**Work with the #y# term.**

**Remember that we factor out #4# so, we have to add #4*4=16# to the right side of the equation.**

**Factor:**

**Perfect square trinomial**

**Perfect square trinomial**