Question

Question #55694

Answer 1

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 `x`s 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.