1/2+(1/3+2/3)+(1/4+2/4+3/4)+.........+(1/100+2/100......+98/100+99/100)
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1/2=1/2×(2-1)
1/3+2/3=1/2×(3-1)
1/4+2/4+3/4=1/2×(4-1)
.............................................
原式=1/2×(2-1)+1/2×(3-1)+1/2×(4-1)+................+1/2×(100-1)
=1/2×(1+2+3+......+99)
=1/2×(1+99)×99×1/2
=1/4×100×99
=25×99
=2475
1/3+2/3=1/2×(3-1)
1/4+2/4+3/4=1/2×(4-1)
.............................................
原式=1/2×(2-1)+1/2×(3-1)+1/2×(4-1)+................+1/2×(100-1)
=1/2×(1+2+3+......+99)
=1/2×(1+99)×99×1/2
=1/4×100×99
=25×99
=2475
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