Question

合并同类项并求值 两道题 二十分悬赏

1.求代数式2t-[t-(t^2-t-3)-2]+(2t^3-3t+1)的值。其中t=1/3
2.化简：(2乘a^5-3乘b^5)-4(1/2 乘a^5-1/2乘a^3乘b^2+2乘a^2乘 b^3-3/4乘 b^5

Answer 1

解：2t-[t-(t^2-t-3)-2]+(2t^3-3t+1)
=2t-(t-t^2+t+3-2)+2t^3-3t+1
=2t-(2t-t^2+1)+2t^3-3t+1
=2t-2t+t^2-1+2t^3-3t+1
=2t^3+t^2-3t
把t=1/3代入得
原式=2×（1/3）^3+（1/3）^2-3×（1/3）
=2/27+1/9-1
=-22/27

追问

题目打错了....是2t-[t-(t^2-t-3)-2]+(2t^2-3t+1)