| 3a+2b+5 | + | 2a- 2b-2 | = 03a+2b+5 = 0 ...（1）2a- 2b-2 = 0 ...（2）两式相加：5a+3= 0,a=3/5由（2）：a-b-1=0b=a-1=-2/52a^2-3ab=a(2a-3b)=3/5(2*3/5+3*2/5)=3/5*11/5=33/25