# How do you simplify (-t+15t^2)-(5t^2+2t-9)?

Simply change the sign to the last three terms and add the same power of $t$:
-t+15t^2-(5t^2+2t−9)= -t+15t^2-5t^2-2t+9
Now, you can sum up the two squares: $15 {t}^{2} - 5 {t}^{2} = 10 {t}^{2}$,
the linear coefficient: $- t - 2 t = - 3 t$,
and obtain the expression $10 {t}^{2} - 3 t + 9$