Câu 1: Tính
a, A = 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + + 1/56 + 1/72
b, B = 1/5.6 + 1/6.7 + 1/7.8 + .... + 1/24.25
a) ( 21/22 + 3/5 + -21/22 ) : 1 2/5 9/17 x 8/5 - 9/17 x 3/5 + 8/17
X - 3/10 = 7/15 x 3/15
\(\dfrac{1}{7}+\dfrac{1}{91}+\dfrac{1}{247}+\dfrac{1}{1475}+\dfrac{1}{7}+\dfrac{1}{1147}\)
\(\dfrac{1}{7}\)+\(\dfrac{1}{91}+\dfrac{1}{247}+\dfrac{1}{1475}+\dfrac{1}{7}+\dfrac{1}{1147}\)
tim x:
1)x-10/3=7/15*3/5
2)8/23.46/24*x=1/3
3)x+3/22=27/121*11/9
4)1-x=49/65*5/7
1) 6/14-(-18)/36-5/15
2) -7/25.39/-14.50/78
3) -3/11.-22/66.121/15
Giúp tớ nhé! Thanks trc!
1/5.6+1/6.7+1/7.8+... +1/x.(x+1)=1/5-x+1/225
1/5.6+1/6.7+1/7.8+... +1/x.(x+1)=1/5-x+1/225
bài 20 : tìm x
\(\dfrac{1}{1.2}\)+\(\dfrac{1}{2.3}\)+...+ \(\dfrac{1}{x.\left(x+1\right)}\)+\(\dfrac{1}{2018.2019}\)
bài 21: tìm x
\(\dfrac{x+1}{99}\)+\(\dfrac{x+2}{98}\)+\(\dfrac{x+3}{97}\)+\(\dfrac{x+4}{96}\)=-4
bài 22: so sánh
a) \(\dfrac{-1}{5}\)+\(\dfrac{4}{-5}\) và 1
b) \(\dfrac{3}{5}\) và \(\dfrac{2}{3}\)+\(\dfrac{-1}{5}\)
c) \(\dfrac{3}{2}\)+\(\dfrac{-4}{3}\) và \(\dfrac{1}{10}\)+\(\dfrac{-4}{5}\)
d)\(\dfrac{1}{2}\)+\(\dfrac{1}{3}\)+\(\dfrac{1}{4}\)+\(\dfrac{1}{5}\)+\(\dfrac{1}{6}\) và 2
