Question

A=2x^2-3xy+y^2+x-3y,B=4x^2-6xy+2y^2+4x-y,若｜x-3a|+(y+3)^2=0,且

Answer 1

因为B-2A=a

将A与B带入

得2x+5y=a

又因为｜x-3a|+(y+3)^2=0

｜x-3a|≥0,(y+3)^2≥0

解得x=3a,y=-3

带入2x+5y=a

a=3

x=9

带入A式

A＝270