M = 1 - 5/6 + 7/2 - 9/20 + 11/30 - 13/42
M = 1/6 + 7/2 - 9/20 + 11/30 - 13/42
M = 22/6 - 9/20 + 11/30 - 13/42
M = 93/60 + 11/30 - 13/42
M = 115/60 - 13/42
M = 4050/2620 = 6/4
M = 1 - 5/6 + 7/2 - 9/20 + 11/30 - 13/42
M = 1/6 + 7/2 - 9/20 + 11/30 - 13/42
M = 22/6 - 9/20 + 11/30 - 13/42
M = 93/60 + 11/30 - 13/42
M = 115/60 - 13/42
M = 4050/2620 = 6/4
so sánh
a)1/2+1/6+1/12+1/20+1/30+1/42 với 60006/70707
b)1/11+1/12+1/13+1/14+.....+1/19+1/20 với 1
c)7/9+8+13 với 8/9+7/13
d)5/6+6/7+7/8+8/5 với 4
B= 3/2-5/6+7/12-9/20+11/30-13/42+15/56-17/72
3/2 - 5/6+ 7/12- 9/20 +11/30-13/42 +15/56 - 17/72+ 19/90
3/2-5/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90
Tính nhanh:
\(\dfrac{1}{6}\) + \(\dfrac{7}{12}\) - \(\dfrac{9}{20}\) + \(\dfrac{11}{30}\) - \(\dfrac{13}{42}\)
1 - 5/6 + 7/12 - 9/20 + 11/30 - 13/42 + 15/56 - 17/72 + 19/90
Gợi ý: tách các mẫu số của các ps đó ra dạng tích
Tính nhanh:
a) 3/5 + 6/11 + 7/13 +2/5 + 16/11 + 19/13
b) 1/2 +1/6 + 1/12 + 1/20 + 1/30 + 1/42
a, 13/19 + 1 - 15/19 - 4/19
b, 3/5 +6/11 +7/13 +2/5 +16/11 +19/13
c, 1/3 +1/6 + 1/12 +1/24 +1/48
d, 1/2 +1/6 +1/12 +1/20 +1/30 +1/42
Tính nhanh tổng:
a, S=1 - 1/5 +7/12 -9/20 + 11/30 - 13/42 + 15/56 + 19/90 - 21/110 + 23/132
b, P=21 * (4/1*3 - 8/3*5 + 12/5*7 - 16/7*9 + ... + 36/17*19 - 40/19*21 ( dấu * là dấu nhân nhé)