已知/a+3/+[2a-b]^2=0,求多项式0.5ab-3a^2+7b^2-2ab+3a^2-8b^2的值

a+3=0,a=-3;
2a-b=0,b=2a=-6;
0.5ab-3a^2+7b^2-2ab+3a^2-8b^2=-b^2-1.5ab=-36-1.5*18=-63

(2a-3b)(3a-2b)+(2a-b)^2+(2ab^2)^3÷8/3*a^3*b^4 =6a -=10a -17ab+10b =10*6-17*(-3) =60+51 =111

/a+3/+[2a-b]^2=0
==》a+3=0 2a-b=0
==>a=-3,b=-6
0.5ab-3a^2+7b^2-2ab+3a^2-8b^2
=0.5ab-2ab-3a^2+3a^2+7b^2-8b^2
=-1.5ab-b^2
=-27-36
=-63

|a＋3|＋(2a－b)²=0
则：a＋3=0且2a－b=0
得：a=－3、b=－6
则：0.5ab－3a²＋7b²－2ab＋3a²－8b²
=－b²－1.5ab
=－(6²)－1.5×(－3)×(－6)
=－36－27
=－63

依题意有：/a+3/=0,得a=-3
2a-b=0,得b=-6
原式=-1.5ab-b^2
=-1.5*(-3)(-6)-(-6)^2
=-63

绝对值和平方都>=0
只能
|a+3|=0 a=-3
[2a-b]^2=0 2a-b=0 b=6
0.5ab-3a^2+7b^2-2ab+3a^2-8b^2
=0.5ab-2ab+3a^2-3a^2+7b^2-8b^2
=-1.5ab-b^2
=1.5*3*6-36
=27-36
=-9