Cho A= 1/2015 +2/2016+3/2017+...+2014/4028 -2014
B = 1/2015+1/2016+1/2017+...+1/4028.
Tính : A/B =?
Cho A = 1/2 + 1/3 + 1/4 + ... + 1/2017 B = 1/2016 + 2/2015 +3/2014+ ...+ 2015/2 + 2016/1 Tính B : A
Ta có: \(\dfrac{B}{A}=\dfrac{\dfrac{1}{2016}+\dfrac{2}{2015}+\dfrac{3}{2014}+...+\dfrac{2015}{2}+\dfrac{2016}{1}}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2017}}\)
\(=\dfrac{1+\left(1+\dfrac{2015}{2}\right)+\left(1+\dfrac{2014}{3}\right)+...+\left(1+\dfrac{2}{2015}\right)+\left(1+\dfrac{1}{2016}\right)}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2017}}\)
\(=\dfrac{\dfrac{2017}{2017}+\dfrac{2017}{2}+\dfrac{2017}{3}+...+\dfrac{2017}{2015}+\dfrac{2017}{2016}}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2017}}\)
\(=\dfrac{2017\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2015}+\dfrac{1}{2016}+\dfrac{1}{2017}\right)}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2015}+\dfrac{1}{2016}+\dfrac{1}{2017}}\)
\(=2017\)
Cho A = 1/2 + 1/3 + 1/4 + ... + 1/2017 B = 1/2015 + 2/2014 +3/2013 + ...+ 2015/2 + 2016/1 Tính B : A
Ta có: \(\dfrac{B}{A}=\dfrac{\dfrac{1}{2016}+\dfrac{2}{2015}+\dfrac{3}{2014}+...+\dfrac{2015}{2}+\dfrac{2016}{1}}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2017}}\)
\(=\dfrac{1+\left(1+\dfrac{2015}{2}\right)+\left(1+\dfrac{2014}{3}\right)+...+\left(1+\dfrac{2}{2015}\right)+\left(1+\dfrac{1}{2016}\right)}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2017}}\)
\(=\dfrac{\dfrac{2017}{2017}+\dfrac{2017}{2}+\dfrac{2017}{3}+...+\dfrac{2017}{2015}+\dfrac{2017}{2016}}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2017}}\)
\(=\dfrac{2017\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2015}+\dfrac{1}{2016}+\dfrac{1}{2017}\right)}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{2015}+\dfrac{1}{2016}+\dfrac{1}{2017}}\)
\(=2017\)
Tính:
A=2019/2018 - 2018/2017 + 2017/2016 - 2016/2015
B=1/2019 - 1/2018 + 1/2017 - 1/2016
C=1/2017 - 1/2016 + 1/2015 - 1/2014
Cho A=1/2+1/3+1/4+...+1/2016+1/2017
B=2016/1+2015/2+2014/3+....+2/2015+1/2016
tính B/A
mọi người giải giúp em em xin cảm ơn ạ :))
a, x+1/2013+x+1/2014+x+1/2015=x+1/2016+x+1/2017
b,x-1/2013+x-2/2014+x-3/2015=x-4/2016-2
tính A=1•2•3•...•2015•2016•(1+1/2+1/3+...+1/2014+1/2015+1/2016)
a chia hết cho 2017
Trong các phân số: -1/2014; 1/-2015; -1/-2016; 1/2017 phân số nhỏ nhất là:
A) -1/2014 B) 1/-2015 C) -1/-2016 D)1/2017
\(\frac{-1}{-2016}=\frac{1}{2016};\frac{1}{-2015}=\frac{-1}{2015}\)
Vì \(\frac{1}{2016};\frac{1}{2017}\)là số dương nên không thể là số lớn nhất.
Có \(\frac{-1}{2014}< \frac{-1}{2015}\)nên \(\frac{-1}{2014}\)là số bé nhất.
ĐÁP ÁN ĐÚNG: A.\(\frac{-1}{2014}\)
Trong các phân số: -1/2014; 1/-2015; -1/-2016; 1/2017 phân số nhỏ nhất là:
A) -1/2014 B) 1/-2015 C) -1/-2016 D)1/2017
So sánh biểu thức sau với 1 :
2015 nhân 2016 - 2
2014 nhân 2015 + 4028
2015* 2016-2= 4,062,238 lớn hơn 1
2014* 2015+4028=4,062,238 lớn hơn 1
\(\frac{2015\times2016-2}{2014\times2015+4028}=\frac{1008-2}{1007+4028}=\frac{1006}{5035}>1\)