Question

A=4x的平方-4xy+y的平方,B=x的平方+xy-5y的平方,求：A-3B；3A+B

Answer 1

A-3B

=(4x²-4xy+y²)-3(x²+xy-5y²)

=(4x²-3x²)+(-4xy-3xy)+(y²+15y²)

=x²-7xy+16y²

3A+B

=3(4x²-4xy+y²)+(x²+xy-5y²)

=(12x²+x²)+(-12xy+xy)+(3y²-5y²)

=13x²-11xy-2y²