问题
选择题
当a=-2时,a2(a4+4a2+16)-4(a4+4a2+16)的值为( )
A.64
B.32
C.-64
D.0
答案
a2(a4+4a2+16)-4(a4+4a2+16)=(a4+4a2+16)(a2-4)=(a4+4a2+16)(a+2)(a-2)
∵a=-2,
∴a+2=0
∴原式=0,
故选D.
当a=-2时,a2(a4+4a2+16)-4(a4+4a2+16)的值为( )
A.64
B.32
C.-64
D.0
a2(a4+4a2+16)-4(a4+4a2+16)=(a4+4a2+16)(a2-4)=(a4+4a2+16)(a+2)(a-2)
∵a=-2,
∴a+2=0
∴原式=0,
故选D.