笨办法硬算:(1-λ)²(2a-λ)+0+0-2(1-λ)(a+5)+4(1-λ)(a+2)=(1-λ)(2a-λ-2aλ+λ²-2a-10+4a+8)=(1-λ)[4a-λ-2aλ+λ²-2] 你要算啥子呀