Question

Subtract:

5x² − 3xy + y² from 7x² − 2xy − 4y²

Answer 1

Change the sign of the term of the expression that is to be subtracted and then add.

Term to be subtracted = 5x² − 3xy + y²
 Changing the sign of each term of the expression gives -5x² + 3xy - y².

On adding:
(7x² − 2xy − 4y²)+(-5x² + 3xy - y²) = 7x² − 2xy − 4y²-5x² + 3xy - y²
= (7-5)x² +(−2+3)xy +(−4-1)y²
= 2x² +xy − 5y²