Question

化简求值：2a-1/3(a^2-b)-1/4(2a^2-a-1/2b),其中a=1/3,b=-1/2

Answer 1

2a-1/3(a^2-b)-1/4(2a^2-a-1/2b),其中a=1/3,b=-1/2
=2a-1/3a^2+1/3b-1/2a^2+1/4a+1/8b
=9/4a-5/6a^2+11/24b
=9/4*1/3-5/6*(1/3)^2+11/24*(-1/2)
=3/4-5/6*(1/9)-11/12
=9/12-5/54-11/12
=-1/6-5/54
=-7/27

Answer 2

2a-1/3(a^2-b)-1/4(2a^2-a-1/2b)

=2a-1/3a^2+1/3b-1/2a^2+1/4a+1/8b
=-5/6a^2+9/4a+11/24b
代值a=1/3,b=-1/2
原式=-5/6*1/9+9/4*1/3-11/24*1/2
=383/432

Answer 3

【1】2a-1/3(a^2-b)-1/4(2a^2-a-1/2b) 【2】=2a-1/3a²+1/3b-1/2a²+1/4a+1/8b【3】=2a-1/4a+1/3b+1/8b-1/3a²-1/2a² 【4】=7/4a+11/24b-5/6a²【5】带入算式=7/4×1/3+11/2×[-1/2]-5/6×1/9 【6】最后结果为=-61/27经过反复计算，结果正确，望采纳！不懂追问