化简求值:5a^2+[2a^2+(5a^2-2a)-2(a^2-3a)],其中a=-1/2

题目

化简求值:5a^2+[2a^2+(5a^2-2a)-2(a^2-3a)],其中a=-1/2

答案

:5a^2+[2a^2+(5a^2-2a)-2(a^2-3a)],
=5a²+2a²+5a²-2a-2a²+6a
=10a²+4a
=10*1/4+4*(-1/2)
=5/2-2
=1/2