Answer:
[tex]-7y^2-13y-18[/tex]
Step-by-step explanation:
[tex](-3y^2-7y-9)-(4y^2+6y+9)[/tex]
To combine like terms we need to remove the parenthesis
Multiply negative inside the second parenthesis
[tex]-3y^2-7y-9-4y^2-6y-9[/tex]
Now combine like terms
The terms that has same variable are like terms
-3y^2 and -4y^2 are like terms so its -7y^2
-7y and -6y are like terms so it becomes -13y
-9 and -9 are like terms so it becomes -18
Answer is [tex]-7y^2-13y-18[/tex]