观察下列各式:1³=1=1/4×1²×2²;1³+2³=9=1/4×2²×3²;1³+2³+3³=36=1/4×3²×4²……,(1)1³+2³+3³+…(n-1)³+n³=________________.(2)计算:①11³+12³+…+99³+100³的值.②2³+4³+6³+…+98³+100³的值.(提示:(2a)³=2³×a³)
问题描述:
观察下列各式:1³=1=1/4×1²×2²;1³+2³=9=1/4×2²×3²;1³+2³+3³=36=1/4×3²×4²……,
(1)1³+2³+3³+…(n-1)³+n³=________________.
(2)计算:①11³+12³+…+99³+100³的值.
②2³+4³+6³+…+98³+100³的值.(提示:(2a)³=2³×a³)
答
1 =1/4×n^2×(n+1)^2
2 1 =100^2×101^2×1/4=25502500
2 =2³(1³+2³+3³……+49³+50³)=8×1/4×50^2×51^2=1625625
答
(1)1³+2³+3³+…(n-1)³+n³=1/4×n³×(n+1)³ (2)①原式=100³+101³=2030301 ②原式=2³(1³+2³+3³……+49³+50³)=1/4×50...