Tuyển Cộng tác viên Hoc24 nhiệm kì 26 tại đây: https://forms.gle/dK3zGK3LHFrgvTkJ6
có ai muốn kb ko fa quá trời
\(A=\frac{1}{1.2}+\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{47.49}\)
\(\Rightarrow2A=1+\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{47.49}\)
ta có: \(\frac{2}{1.3}=1-\frac{1}{3}\)
\(\frac{2}{3.5}=\frac{1}{3}-\frac{1}{5}\)
...
\(\frac{2}{47.49}=\frac{1}{47}-\frac{1}{49}\)
vậy \(2A=1+1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{45}-\frac{1}{47}+\frac{1}{47}-\frac{1}{49}\)
\(\Rightarrow2A=2-\frac{1}{49}\)
\(\Rightarrow2A=\frac{97}{49}\)
\(\Rightarrow A=\frac{97}{98}\)
Cmr 7/12 < A< 5/6
Biết A=1-1/2+1/3-1/4+...+1/47-1/48+1/49-1/50
Cmr 7/12 < A< 5/6
Biết A=1-1/2+1/3-1/4+...+1/47-1/48+1/49-1/50
Cmr 7/12 < A< 5/6
Biết A=1-1/2+1/3-1/4+...+1/47-1/48+1/49-1/50
Tính S/P biết:
S = 1/2 + 1/3 + 1/4 + 1/5 + ... + 1/49 + 1/50
P = 1/49 + 2/48 + 3/47 + ... + 48/2 +49/1
a)11/53+(32/47+-10/53)+-64/94+1/53+1/3
b) (-1+45/115+47/51)+(-9/23+-1/3)
c) -13/49+12/48+1/12+3/18
d) 13/15+(-4/5+7/18)+-5/12+1/16
A) A= - ( 5 - 6 ) - ( 3-4+5-7)
B) P = ( 1+3+5+...+47+49)-(2+4+6+...+48+50)
so sánh giữa s và p biết
s=1/2+1/3+1/4+1/5+.............+1/49
p=1/49+2/48+3/47+4/46+5/45+...........+49/1
1/1*2*3*4+1/2*3*4*5+1/3*4*5*6+...+1/47*48*49*
50
tính nhanh
a) 99 - 97 + 95 - 93 + 91 -89 + ... +7-5+3-1
b) 50-49+48-47+46-45+...+4-3+2-1
