\(x-25\%.x=\dfrac{1}{2}\\ x.1-\dfrac{1}{4}.x=\dfrac{1}{2}\\ x\left(1-\dfrac{1}{4}\right)=\dfrac{1}{2}\\ x.\dfrac{3}{4}=\dfrac{1}{2}\\ x=\dfrac{1}{2}:\dfrac{3}{4}=\dfrac{1}{2}.\dfrac{4}{3}\\ x=\dfrac{2}{3}\)
\(\text{Tìm x, biết:}\)
\(a\)) \(x-\dfrac{2}{3.5}-\dfrac{2}{5.7}-\dfrac{2}{7.9}-\dfrac{2}{9.11}-\dfrac{2}{11.13}-\dfrac{2}{13.15}=\dfrac{2}{5}\)
\(b\)) \(\dfrac{1}{2.3}.x+\dfrac{1}{3.4}.x+\dfrac{1}{4.5}.x+...+\dfrac{1}{49.50}.x=1\)
\(c\)) \(x-\dfrac{20}{11.3}-\dfrac{20}{13.15}-...-\dfrac{53}{55}=\dfrac{3}{11}\)
\(d\)) \(x+\dfrac{4}{5.9}+\dfrac{4}{9.13}+...+\dfrac{4}{41.45}=\dfrac{-37}{45}\)
\(e\)) \(\left(\dfrac{11}{12}.\dfrac{11}{2.23}.\dfrac{11}{23.34}...\dfrac{11}{89.100}\right).x=\dfrac{5}{3}\)
\(f\)) \(\left(\dfrac{2}{11.13}.\dfrac{2}{13.15}.\dfrac{2}{15.17}...\dfrac{2}{19.21}\right)-x+4+\dfrac{221}{231}=\dfrac{7}{3}\)
a) Tính A = ( 1 - \(\dfrac{1}{2}\) )( 1 - \(\dfrac{1}{3}\) ) (1-\(\dfrac{1}{4}\) ) ....(1-\(\dfrac{1}{2014}\) ) (1-\(\dfrac{1}{2015}\) ) (1-\(\dfrac{1}{2016}\) )
b)Tìm x biết \(\dfrac{x-2}{12}\) + \(\dfrac{x-2}{20}\) + \(\dfrac{x-2}{30}\)+ \(\dfrac{x-2}{42}\) + \(\dfrac{x-2}{56}\) +\(\dfrac{x-2}{72}\) = \(\dfrac{16}{9}\)
tìm số nguyên x,y biết:
\(\dfrac{1}{x}-\dfrac{1}{y}=\dfrac{1}{2}\)
\(Tìm\) \(x\)∈\(Z\)\(,\) \(biết\)\(:\)
\(a\)) \(\left(x-20\right)+\left(x-19\right)+\left(x-18\right)+...+99+100=100\)
\(b\)) \(213-x.\left(\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2020}}\right):\left(1-\dfrac{1}{2^{2020}}\right)=13\)
Tìm \(x,y\in N\):
a) 32x+1 . 7y = 9 . 21x
b) \(\dfrac{27^x}{3^{2x-y}}=243\) và \(\dfrac{25^x}{5^{x+y}}=125\)
Tìm x,y biết \(\dfrac{1-2y}{18}=\dfrac{1+4y}{24}=\dfrac{1+6y}{6x}\)
Tìm x,y,z biết \(\dfrac{x}{3}=\dfrac{y}{4}\) ; \(\dfrac{y}{5}=\dfrac{z}{7}\) và x+y+z =9^2
Tìm n để A= 12n^2 - 5n -25 là số nguyên tố
Tìm \(x\):
\(\dfrac{x}{7}-\dfrac{7}{8}=\dfrac{-25}{56}\)
\(\text{Tìm x, biết:}\)
\(20\text{%}x-x+\dfrac{1}{5}=\dfrac{3}{4}\)
1. Tìm x, biết:
a, \(1\dfrac{3}{5}\) + \(\dfrac{\dfrac{2}{7}+\dfrac{2}{17}+\dfrac{2}{37}}{\dfrac{5}{7}+\dfrac{5}{17}+\dfrac{5}{37}}\) . x = \(\dfrac{16}{5}\)
b, (\(\dfrac{1}{24.25}\) + \(\dfrac{1}{25.26}\) + . . . + \(\dfrac{1}{39.40}\) ) . 120 + x. \(\dfrac{1}{3}\) = -4
c, \(\left|x-\dfrac{1}{3}\right|\) . 2 + \(\dfrac{4}{5}\) = 0,24
d, \(\dfrac{24}{7x-3}\) = \(\dfrac{-4}{25}\)
e, ( 50% x + \(5\dfrac{1}{4}\) ) , \(\dfrac{-2}{3}\) = \(2\dfrac{5}{6}\)
f, \(1\dfrac{1}{3}\) - 25%\(\dfrac{-5}{12}\) + 2x = 1,6 : \(\dfrac{3}{5}\)
