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1x2十2x3十3x4十……十10x11(写出过程)

1*2=1*3(1*2*3-0*1*2)2*3=1/3(2*3*4-1*2*3).10*11=1/3(10*11*12-9*10*11)所以1x2+2x3+3x4+···+10x11=1/3(10*11*12-0*1*2)=440

原式=1-1/2+1/2-1/3+1/3-1/4 +1/10-1/11=1-1/11=10/11

1×2+2×3+3×4+...+n×(n+1) = (1/3)×[1×2×3 - 0×1×2] +(1/3)×[2×3×4 - 1×2×3] +(1/3)×[3×4×5 - 2×3×4] +... +(1/3)×[n×(n+1)×(n+2) - (n-1)×n×(n+1)] = (1/3)×n×(n+1)×(n+2) [2] 相邻三个正整数乘积和 1×2×3+2×3×4+3×4×5+...+n×(n+1)×...

1x2+2x3+3x4+4x5+……+n(n+1) =1²+2²+3²+...........+n²+(1+2+3+.....+n) =n(n+1)(2n+1)/6+n(n+1)/2 =n(n+1)(n+2)/3 1x2+2x3+3x4+4x5+……+10x11 =10×11×12/3 =440

(1)=2+6+12+20+30+42+56+72+90+110=440

我小学都没毕业。俺不懂 1.M等于一,N等于负4. 其他的不懂。这些奥数题!!!!!

1x2x3x4x5x6x7x8x9x10x11÷(27X25X24X22) =(3×9÷27)×(5×10÷25)×(4×6÷24)×(2×11÷22)×7×8 =1×2×1×1×56 =112

(x+1)(x+2)(x+3)(x+4)+1 =(x+1)(x+4)(x+2)(x+3)+1 =(x²+5x+4)(x²+5x+6)+1 =[(x²+5x+5)-1][(x²+5x+5)+1]+1 =[(x²+5x+5)²-1]+1 =(x²+5x+5)²-1+1 =(x²+5x+5)² 所以9x10x11x12十1 =(8+1)(8+2)(8+...

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