Question 41475
(8y^2-2y-3) - (9y^2-7y-1)
Arrange the polynomials horizontally.  Place like-terms underneath like-terms: 

 
(8y^2-2y-3)
-(9y^2-7y-1)
____________
.
.

Next remove the parenthesis from the second polynomial and multiply it through by (-1).
.
(8y^2-2y-3)
-(9y^2-7y-1)
____________
.
.
+8y^2-2y-3
-9y^2+7y+1
____________
.
.

Perform the indicated operations:

+8y^2-2y-3
-9y^2+7y+1
____________
-1y^2+5y-2
.
.
Check your answer by adding the answer to one of the polynomials.
.
9y^2-7y-1
-1y^2+5y-2
__________
8y^2-2y-3