Question

已知A=2x^2-3xy+y^2+2x+2y,B=4x^2-6xy+2y^2-3x-y

Answer 1

B-2A=4x²-6xy+2y²-3x-y-2(2x²-3xy+y²+2x+2y)

=-7x-5y

1.当x=2,y=-1/5时

B-2A=-14+1=-13

2.|x-2a|+(y-3)²=0

∴x-2a=0 y-3=0

x=2a y=3

B-2A=-14a-15=a

a=-1