Question #55694

1 Answer
Aug 22, 2016

They combined the like terms.

Explanation:

Let's begin at 16/9y^2+y^2=25. We can see that both terms on the left have a y^2:
16/9color(red)(y^2)+color(red)(y^2)=25

Recall from algebra that we can combine these like terms. It's the same idea as this:
x+x+x=9
3x=9->x=3

You can add the three xs together to get 3x. In your example, we're going to add the 16/9y^2 and the y^2 together:
16/9y^2+y^2=25
(16y^2)/9+(9y^2)/9=25 (16/9y^2 and (16y^2)/9 are the same thing)
(25y^2)/9=25 or 25/9y^2=25

As you can see, we just added the fractions.