问题
解答题
先化简,再求值:(a-2)(a+2)+3(a+2)2-6a(a+2),其中a=5.
答案
(a-2)(a+2)+3(a+2)2-6a(a+2)
=a2-4+3a2+12a+12-6a2-12a
=-2a2+8,
当a=5时,原式=-2×52+8=-42.
先化简,再求值:(a-2)(a+2)+3(a+2)2-6a(a+2),其中a=5.
(a-2)(a+2)+3(a+2)2-6a(a+2)
=a2-4+3a2+12a+12-6a2-12a
=-2a2+8,
当a=5时,原式=-2×52+8=-42.