5a的平方-【3a-2[2a-3}-4a的平方】其中a等于-2/1
问题描述：
5a的平方-【3a-2[2a-3}-4a的平方】其中a等于-2/1
答
5a^2-[3a-2(2a-3)-4a^2]
=5a^2-(3a-4a+6-4a^2)
=5a^2-(-a+6-4a^2)
=5a^2+a-6+4a^2
=9a^2+a-6
当a=-1/2时
原式=9×(-1/2)^2-1/2-6
=9/4-1/2-6
=-17/4
答
5a²-[3a-2(2a-3)-4a²]
=5a²+4a²+a-6
=9a²+a-6
=9/4-1/2-6
=-17/4
答
5a的平方-【3a-2[2a-3}-4a的平方】
=5a²-3a+4a-6+4a²
=9a²+a-6 a等于-1/2
=9*(-1/2)²-1/2-6
=9/4-2/4-6
=7/4-24/4
=-17/4