先化简,再求值：3(a-1)^2-(2a+1)(a-2),其中a=-3/4

先化简,再求值：3(a-1)^2-(2a+1)(a-2),其中a=-3/4
先化简,再求值：3(a-1)^2-(2a+1)(a-2),其中a=-3/4

先化简,再求值：3(a-1)^2-(2a+1)(a-2),其中a=-3/4
直接拆吧,貌似只能这样了

3(a-1)^2-(2a+1)(a-2)
=3a^2+3-6a-2a^2+4a-a+2
=a^2-3a+5
=45/16+5
=125/16

3(a-1)^2-(2a+1)(a-2)
=3(a^2-2a+1)-(2a^2-3a-2)
=3a^2-6a+3-2a^2+3a+2
=a^2-3a+5
a=-3/4
=125/16

化简结果为 a^2-3a+5，代值结果为125/16