ax^+2xy-x-(3x^-1/2bxy+3y)=ax^+2xy-x-3x^+1/2bxy-3y=(a-3)x^2+(2+1/2b)xy-x-3y不含两项式,即a-3=0,a=32+b/2=0,b=-4a^2-2b=9-2(-4)=17