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\(A=2^{2017}-(2^{2016}+2^{2015}+......+2^1+2^0)\)
Đặt \(B=2^{2016}+2^{2015}+.....+2^1+2^0\)
\(\Rightarrow2B=2^{2017}+2^{2016}+....+2^1+2^0\)
\(\Rightarrow2B-B=(2^{2017}+2^{2016}+...+2^0)-(2^{2016}+2^{2015}+...+2^1+2^0)\)
\(\Rightarrow B=2^{2017}-2^0\)
\(\Rightarrow A=2^{2017}-(2^{2017}-1)\)
\(\Rightarrow A=1\)
2A = 22018 - (22017 + 22016 + ....+ 21)
2A - A = [22018 - (22017 + 22016 + ....+ 21 )] - [22017 - (22016 + 22015 +..... + 21 + 20)
A = 22018 - 22017 - 22017 - 1
A = 22018 - (22017 +22017 +1)
A = 22018 - (22018 +1 )
A = -1
1/2 + 1/3 + 1/4 + ...............+ 1/2017 + 1/2018 PHẦN 1/2017 + 2/2016 + 3/2015 + 2017/1 đấy nha !
Bài 1:
a) b) c) sẽ có bạn giải cho em thôi vì nó dễ tính tay cũng đc
d) \(\frac{4}{2.5}+\frac{4}{5.8}+...+\frac{4}{23.26}\)
\(=\frac{4}{3}.\left(\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{23.26}\right)\)
\(=\frac{4}{3}.\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{23}-\frac{1}{26}\right)\)
\(=\frac{4}{3}.\left(\frac{1}{2}-\frac{1}{26}\right)\)
\(=\frac{4}{3}.\frac{6}{13}\)
\(=\frac{8}{13}\)
Bài 2:
a) b) c)
d)\(|\frac{5}{8}x+\frac{6}{7}|-\frac{4}{7}=\frac{10}{7}\)
\(\Leftrightarrow|\frac{5}{8}x+\frac{6}{7}|=2\)
\(\Leftrightarrow\orbr{\begin{cases}\frac{5}{8}x+\frac{6}{7}=2\\\frac{5}{8}x+\frac{6}{7}=-2\end{cases}}\)\(\Leftrightarrow\orbr{\begin{cases}\frac{5}{8}x=\frac{8}{7}\\\frac{5}{8}x=\frac{-20}{7}\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{64}{35}\\x=\frac{-32}{7}\end{cases}}}\)
Vậy \(x\in\left\{\frac{64}{35};\frac{-32}{7}\right\}\)
Bài 1 :
a) \(\left(\frac{2}{5}-\frac{5}{8}\right):\frac{11}{30}+\frac{1}{8}\)
\(=\frac{-9}{40}:\frac{11}{30}+\frac{1}{8}\)
\(=\frac{-27}{44}+\frac{1}{8}\)
\(=\frac{-43}{88}\)
a, \(6\frac{5}{7}-\left(1\frac{3}{4}+2\frac{5}{7}\right)=6\frac{5}{7}-1\frac{3}{4}-2\frac{5}{7}=6\frac{5}{7}-2\frac{5}{7}-\frac{7}{4}=4-\frac{7}{4}=\frac{16}{4}-\frac{7}{4}=\frac{9}{4}\)
b, (-4/5+4//3)+(-5/4+14/5)-7/3 = -4/5+4/3+-5/4+14/5-7/3=(-4/5+14/5)+(4/3-7/3)+-5/4=2+(-1)+-5/4=1+-5/4=-1/4
Phần b dấu ''/'' là dấu phần nha , mk viết ra phân số thì nó dài quá nên mk viết vậy , t.i.c.k mk hennnn ^^ thanks @@
Nếu thích kb qua face vs mk nick : Akiko Ayano nhé . Kb và ib nch vs nhau nè
Ta có: 2017 -1/4 -2/5 -3/6 -... -2017/2020
= (1-1/4)+(1-2/5)+(1-3/6)+...+(1-2017/2020)
= 3/4 + 3/5 + 3/6 +...+ 3/2020
= 15 (1/20+ 1/25+ 1/30+...+ 1/10100)
Vậy B = 15.
Chúc bạn học tốt.
\(B=\frac{2018+2019}{2019+2020}\)
\(\Rightarrow B=\frac{2018}{2019+2020}+\frac{2019}{2019+2020}\)
\(\Rightarrow B< \frac{2018}{2019}+\frac{2019}{2020}=A\)
Vậy B < A
\(B=\frac{2015+2016+2017}{2016+2017+2018}\)
\(\Rightarrow B=\frac{2015}{2016+2017+2018}+\frac{2016}{2016+2017+2018}+\frac{2017}{2016+2017+2018}\)
\(\Rightarrow B< \frac{2015}{2016}+\frac{2016}{2017}+\frac{2017}{2018}=A\)
Vậy B < A
= 1 + 1 + 1 + ... + 1 - 2017 (1008 số 1)
= 1008 - 2017 = - 1009
\(A=4^{2017}+4^{2016}+...+4^2+4+1\)
\(4A=4^{2018}+4^{2017}+...+4^3+4^2+4\)
\(4A-A=\left(4^{2018}+4^{2017}+...+4^3+4^2+4\right)-\left(4^{2017}+...+4+1\right)\)
\(3A=4^{2018}-1\)
\(A=\frac{4^{2018}-1}{3}\)