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31 1/2×2/3 4 1/3×3/4 51 1/4×4/5

    发布时间:2018-07-26 20:23

    n^2 -(n+1)^2
    =-2n-1
    1²-2²+3²-4²+5²-6²+……-50²+51²
    =(1²-2²)+(3²-4²)+(5²-6²)+……+(49²-50²)+51²
    =-3-7-11-...-99 +51²
    =-(3+99)25/2 +51²
    =51² -1275
    =1326

    回复:

    =(4²-1)+(6²-1)+(8²-1)+……+(50²-1)
    =(4²+6²+8²+……+50²)-(1+1+1+……+1)
    =(4×2²+4×3²+4×4²+……+4×25²)-24
    =4×(2²+3²+4²+……+25²)-24
    =4×(25×26×51÷6-1²)-24
    =22096-24
    =22072

    回复:

    =124/3×3/4+205/4×4/5
    =31+41
    =72

    回复:

    n^2 -(n+1)^2 =-2n-1 1²-2²+3²-4²+5²-6²+……-50²+51² =(1²-2²)+(3²-4²)+(5²-6²)+……+(49²-50²)+51² =-3-7-11-...-99 +51² =-(3+99)25/2 +51² =5...

    回复:

    1×(100-1)+2×(100-2)+3×(100-3)+4×(100-4)...=(1+2+3+4...+49)*100-1²-2²-3²..-49²=(1+49)*49*100/2-1²-2²-3²=50*100/2-1/6*49*(49+1)*(2*49+1)=82075

    回复:

    =(4²-1)+(6²-1)+(8²-1)+……+(50²-1) =(4²+6²+8²+……+50²)-(1+1+1+……+1) =(4×2²+4×3²+4×4²+……+4×25²)-24 =4×(2²+3²+4²+……+25²)-24 =4×(25×26×5...

    回复:

    积分为: ln|x+1|+C

    回复:

    =124/3×3/4+205/4×4/5 =31+41 =72

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