当a=2时,多项式2a^2-3a-4a^2+5a-1=_________

问题描述:

当a=2时,多项式2a^2-3a-4a^2+5a-1=_________

2a^2-3a-4a^2+5a-1
=-2a²+2a-1
=-8+4-1
=-5