Tính nhanh
1/1.1/2+1/2.1/3+1/3.1/4+ ... + 1/99 .1/100
1/2 + 1/6 + 1/12 + 1/20 + ...+ 1/110
2/1.3 + 2/3.5 + 2/5.7 +... +2/99.101
7/1.3 + 7/3.5 + 7/5.7 + .....+7/99.101
3/10 + 3/40 + 3/88 + ... +3/340
Tìm x
-3x - 1/5 = 1/2 -x
4-3x-3/6= -2x + 1/2
-2(x-1/4) - 3x = 1/6
1/3 - 1/2(4x - 1) = 3/2 - x
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Sinh Học lớp 12
