Question

Subtract:

x³ + 2x²y + 6xy² − y³ from y³ − 3xy² − 4x²y

Answer 1

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

Term to be subtracted = x³ + 2x²y + 6xy² − y³
 Changing the sign of each term of the expression gives -x³ - 2x²y - 6xy² + y³.
On adding:
(y³ − 3xy² − 4x²y)+(-x³ - 2x²y - 6xy² + y³) = y³ − 3xy² − 4x²y-x³ - 2x²y - 6xy² + y³
= -x³ +(- 2-4)x²y +(-6-3)xy² + (1+1)y³
= -x³ - 6x²y - 9xy² + 2y³