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\(S=2^{2010}-2^{2009}-2^{2008}-...-2-1\)
\(S=2^{2010}-\left(2^{2009}+2^{2008}+...+2+1\right)\)
Đặt \(A=1+2+...+2^{2008}+2^{2009}\)
\(\Rightarrow2A=2+2^2+..+2^{2010}\)
\(\Rightarrow A=2^{2010}-1\)
\(\Rightarrow S=2^{2010}-\left(2^{2010}-1\right)\)
\(\Rightarrow S=1\)
S = 22010 - 22009 - 22008 - ... - 2 - 1
S= 22010 - ( 22009 + 22008 + ... + 2 + 1 )
Đặt A = 22009 + 22008 + .... + 2 + 1
2A = 2 . ( 22009 + 22008 + .... + 2 + 1
2A = 22010 + 22009 + .... + 22 + 2
2A - A = 22010 + 22009 + ...... + 22 + 2 - 22009 - 22008 - .... - 2 - 1
A = 22010 - 1
Thay A vào S ta có :
S = 22010 - ( 22010 - 1 )
S = 22010 - 22010 + 1
S = 0 + 1
S = 1
Vậy S = 1
\(a,\frac{x+5}{2010}+\frac{x+6}{2009}+\frac{x+7}{2008}=-3\)
\(\Rightarrow\left(\frac{x+5}{2010}+1\right)+\left(\frac{x+6}{2009}+1\right)+\left(\frac{x+7}{2008}+1\right)=0\)
\(\Rightarrow\frac{x+2016}{2010}+\frac{x+2016}{2009}+\frac{x+2006}{2008}=0\)
chỉ bt lm v thoi "(
a) \(\frac{x+5}{2010}+\frac{x+6}{2009}+\frac{x+7}{2008}=-3\)
<=> \(\frac{x+5}{2010}+1+\frac{x+6}{2009}+1+\frac{x+7}{2008}+1=0\)
<=> \(\frac{x+2015}{2010}+\frac{x+2015}{2009}+\frac{x+2015}{2008}=0\)
<=> \(\left(x+2015\right)\left(\frac{1}{2010}+\frac{1}{2009}+\frac{1}{2008}\right)=0\)
<=> \(x+2015=0\) (do 1/2010 + 1/2009 + 1/2008 # 0 )
<=> \(x=-2015\)
Vậy...
b) mạo phép chỉnh đề
\(\frac{x+2}{327}+\frac{x+3}{326}+\frac{x+4}{325}+\frac{x+344}{5}=0\)
<=> \(\frac{x+2}{327}+1+\frac{x+3}{326}+1+\frac{x+4}{325}+1+\frac{x+344}{5}-3=0\)
<=> \(\frac{x+329}{327}+\frac{x+329}{326}+\frac{x+329}{325}+\frac{x+329}{5}=0\)
làm tương tự a
a, \(\left(x-1\right).\left(x+2\right)\)\(>0\Rightarrow\orbr{\begin{cases}x-1< 0;x+2< 0\left(loai\right)\Rightarrow x< 1\\x-1>0;x+2>0\Rightarrow x>1;x>-2\end{cases}}\)
=> -2 < x < 1
Câu b và câu d làm tương tự nha bạn(Câu b thì xét khác dấu)
\(S=2^{2010}-2^{2009}-2^{2008}-...-2-1\)
\(\Rightarrow2S=2.\left(2^{2010}-2^{2009}-2^{2008}-...-2-1\right)\)
\(\Rightarrow2S=2^{2011}-2^{2010}-2^{2009}-...-2^2-2\)
Có \(2S-S=\left(2^{2011}-2^{2010}-2^{2009}-...-2^2-2\right)-\left(2^{2010}-2^{2009}-2^{2008}-...-2-1\right)\)
\(S=2^{2011}-2^{2010}-2^{2009}-...-2^2-2-2^{2010}+2^{2009}+2^{2008}+...+2+1\)
\(S=2^{2011}+1\)
Bài 1
\(=-\frac{21}{60}=-\frac{7}{20}\)
\(b,\left(2-\frac{1}{3}\right)^2+|-\frac{5}{6}|+\frac{-7}{12}-\frac{25}{9}\)
\(=\frac{25}{9}+\frac{5}{6}-\frac{7}{12}-\frac{25}{9}\)
\(=\left(\frac{25}{9}-\frac{25}{9}\right)+\left(\frac{5}{6}-\frac{7}{12}\right)\)
\(=0+\frac{1}{4}=\frac{1}{4}\)
Bài 2
\(a,x+\frac{2}{5}=-\frac{3}{10}\)
\(x=-\frac{3}{10}-\frac{2}{5}\)
\(x=-\frac{3}{10}-\frac{4}{10}\)
\(x=-\frac{7}{10}\)
\(b,|\frac{2}{3}+x|=\frac{5}{7}\)
\(\Rightarrow\orbr{\begin{cases}\frac{2}{3}+x=\frac{5}{7}\\\frac{2}{3}+x=-\frac{5}{7}\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{5}{7}-\frac{2}{3}\\x=-\frac{5}{7}-\frac{2}{3}\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{1}{21}\\x=-\frac{29}{21}\end{cases}}}\)
== chắc trog quá trình lm lỡ xóa đó
\(a,-\frac{3}{4}.\frac{7}{15}\)
\(=-\frac{21}{60}=-\frac{7}{20}\)
với lại bài trên mk tính nhẩm ko bấm máy sai == sửa giúp
Bài 1 :\(a,=\frac{4}{1.3}.\frac{9}{2.4}.\frac{16}{3.5}...\frac{100^2}{99.101}\)
\(=\frac{2.3.4...100}{1.2.3...99}.\frac{2.3.4...100}{3.4...101}\)
\(=100.\frac{2}{101}=\frac{200}{101}\)
a, Đặt \(A=2^{2010}+2^{2009}+2^{2008}+...+2^1+2^0\)
\(\Rightarrow2A=2^{2011}+2^{2010}+2^{2009}+...+2^2+2^1\)
\(\Rightarrow2A-A=2^{2011}-2^0\)
\(\Rightarrow A=2^{2011}-1\)
b,\(7^{x+2}+2.7^{x-1}=345\)
\(7^{x-1}.\left(7^3+2\right)=345\)
\(\Rightarrow7^{x-1}.345=345\)
\(\Rightarrow7^{x-1}=345:345=1\)
\(\Rightarrow7^{x-1}=7^0\)
\(\Rightarrow x-1=0\)
\(\Rightarrow x=1\)
Vậy \(x=1\)
Thanks bạn nhen . Hi hi.