Tính nhanh:7/2+7/6+7/12+7/20+7/30+7/42+7/56+7/72+7/90+7/110
7/2+7/6+7/12+7/20+7/30+7/42+7/56+7/72+7/90+7/110
đây là dạng tính nhanh nào?
làm thế nào
\(\frac{7}{2}+\frac{7}{6}+\frac{7}{12}+\frac{7}{20}+\frac{7}{30}+\frac{7}{42}+\frac{7}{56}+\frac{7}{72}+\frac{7}{90}\)
B= 3/2-5/6+7/12-9/20+11/30-13/42+15/56-17/72
\(\frac{7}{2}+\frac{7}{6}+\frac{7}{12}+\frac{7}{20}+\frac{7}{30}+\frac{7}{42}\)
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
Giai giup minh bai toan tinh nhanh nay nhe
a) 7/4+7/28+7/70+7/130
b) 99/98-98/97+1/97×98
c) 51×115+37×102-17×45-37×2
d) 10+1/90-1/72-1/56-1/42-1/30-1/20-1/6-1/2
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
