Question

已知A=4x的平方-5XY+Y平方B=X平方+3XY-5Y平方

Answer 1

解

A-2B

=(4x²-5xy+y²)-2(x²+3xy-5y²)

=(4x²-2x²)+(-5xy-6xy)+(y²+10y²)

=2x²-11xy+11y²

-2A+3B

=-2(4x²-5xy+y²)+3(x²+3xy-5y²)

=(-8x²+3x²)+(10xy+9xy)+(-2y²-15y²)

=-5x²+19xy-17y²