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Cho A = 2010/2009 + 2011/2010 + 2012/2011 + 2013/2012 + 2014/2013 + /2015/2014 + 2016/2015 + 2017/2016.
Hãy so sánh A với 8
mk vote 5 sao, bên trên là phân số
Tìm x biết: 100% : x – 50% : x + 40% : 30% : x = 18
nhanh lên một chút nhé các bn
Ta có:
$A=\frac{2010}{2009}+\frac{2011}{2010}+\frac{2012}{2011}+\frac{2013}{2012}+\frac{2014}{2013}+\frac{2015}{2014}+\frac{2016}{2015}+\frac{2017}{2016}=8,00398$
mà $8,00398>8$
$\Rightarrow A>8$
100%:x-50%:x+40%:30%:x=18 (ĐK:$x\neq 0$)
$\Leftrightarrow \frac{100}{100}:x-\frac{50}{100}.\frac{1}{x}+\frac{40}{100}:\frac{30}{100}.\frac{1}{x}=18\\\Leftrightarrow 1:x-\frac{1}{2}.\frac{1}{x}+\frac{40}{100}.\frac{100}{30}.\frac{1}{x}=18\\\Leftrightarrow \frac{1}{x}-\frac{1}{2x}+4.\frac{1}{3}.\frac{1}{x}=18\\\Leftrightarrow \frac{11}{6x}=18\\\Leftrightarrow 11=108x\\\Leftrightarrow x=\frac{11}{108}$
Vậy $x=\frac{11}{108}$