Answer:
you multiplied the expression by √(y+9), changing its value
Step-by-step explanation:
The appropriate multiplier is 1, in the form of something that will remove the radical from the denominator. Here, that something is ...
[tex]1=\dfrac{\sqrt{y+9}}{\sqrt{y+9}}[/tex]
Then the appropriate form is ...
[tex]\dfrac{3y}{\sqrt{y+9}}=\dfrac{3y}{\sqrt{y+9}}\cdot\dfrac{\sqrt{y+9}}{\sqrt{y+9}}=\dfrac{3y\sqrt{y+9}}{y+9}[/tex]
