Answer:
[tex]-6t^2+t+1[/tex]
Step-by-step explanation:
First off, this is an addition problem, so the parenthesis are unnecessary. Remove them and group the like terms next to each other, just for ease:
[tex]3t^2-9t^2+6t-5t+1[/tex]
Combining like terms gives you
[tex]-6t^2+t+1[/tex]
