(2a+3b)²+(3a-b)²,其中a=1/2 b=-1/2先化简,在求值（代入）

(2a+3b)²+(3a-b)²,其中a=1/2 b=-1/2先化简,在求值（代入）
(2a+3b)²+(3a-b)²,其中a=1/2 b=-1/2
先化简,在求值（代入）

(2a+3b)²+(3a-b)²,其中a=1/2 b=-1/2先化简,在求值（代入）
(2a+3b)²+(3a-b)²
=4a²+12ab+9b²+9a²-6ab+b²
=13a²+6ab+10b².
a=1/2,b=-1/2
即a=-b=1/2
a=-b时,(2a+3b)²+(3a-b)²=13a²+6ab+10b²=13a²-6a²+10a²=17a²=17/4.
注：a=1/2,b=-1/2时,2a+3b=-1/2,3a-b=-2
(2a+3b)²+(3a-b)²=1/4+4=17/4
不化简求起来更容易的.

(2a+3b)²+(3a-b)²

=4a²+9b²+12ab+9a²+b²-6ab

=13a²+10b²+6ab
,其中a=1/2 b=-1/2
=13/4 +10/4 -6/4
= (13+10-6)/4
= 17/4

(2a+3b)²+(3a-b)²
=4a²+9b²+12ab+9a²+b²-6ab
=13a²+10b²+6ab
=13x1/4+10x1/4-6x1/4
=1/4x(13+10-6)
=1/4x17
=17/4

题目是这样的吗
这还不如先带进去，再求值呢