设A=2x²-3xy+y²+x-3y,B=4x²-6xy+2y²+4x-y,若|x-3a|+(y+3)²=0且B-2A=a,求A的值

设A=2x²-3xy+y²+x-3y,B=4x²-6xy+2y²+4x-y,若|x-3a|+(y+3)²=0且B-2A=a,求A的值
设A=2x²-3xy+y²+x-3y,B=4x²-6xy+2y²+4x-y,若|x-3a|+(y+3)²=0且B-2A=a,求A的值

设A=2x²-3xy+y²+x-3y,B=4x²-6xy+2y²+4x-y,若|x-3a|+(y+3)²=0且B-2A=a,求A的值
|x-3a|+(y+3)²=0
x-3a=0 y+3=0
x=3a y=-3
B-2A
=4x²-6xy+2y²+4x-y-2(2x²-3xy+y²+x-3y)
=2x+5y
=2*3a-15
=a
a=3