已知x-y=-3,xy=2則3x-5y-(x-3y-4xy)是多少

已知x-y=-3,xy=2則3x-5y-(x-3y-4xy)是多少

3x-5y-(x-3y-4xy)
=3x-5y-x+3y+4xy
=2x-2y+4xy
=2(x-y)+4xy
=2×(-3)+4×2
=-6+8
=2