tìm x biết \(\dfrac{6}{5}\) <x-\(\dfrac{3}{2}\) <\(\dfrac{12}{5}\)
Tìm x biết :
\(x+\dfrac{1}{2}=\dfrac{33}{4}\)
\(\dfrac{5}{6}-x=\dfrac{1}{3}\)
\(x+\dfrac{4}{5}=\dfrac{-2}{3}\)
\(x+\dfrac{1}{2}=\dfrac{33}{4}\\ \Rightarrow x=\dfrac{33}{4}-\dfrac{1}{2}\\ \Rightarrow x=\dfrac{31}{4}\\ \dfrac{5}{6}-x=\dfrac{1}{3}\\ \Rightarrow x=\dfrac{5}{6}-\dfrac{1}{3}\\ \Rightarrow x=\dfrac{1}{2}\\ x+\dfrac{4}{5}=\dfrac{-2}{3}\\ \Rightarrow x=\dfrac{-2}{3}-\dfrac{4}{5}\\ \Rightarrow x=\dfrac{-22}{15}\)
Tìm x biết:
(50%.x+5\(\dfrac{1}{4}\)).\(\dfrac{-2}{3}\)=2\(\dfrac{5}{6}\)
`(50% . x+5 1/4) . (-2/3) = 2 5/6`
`(1/2 x + 21/4) . (-2/3) = 17/6`
`1/2 x + 21/4 = -17/4`
`1/2 x = -19/2`
`x=-19`
\(^{^{tham}}\) \(^{^{khảo}}\)
\(\left(50\%.+5\dfrac{1}{4}\right).\left(-\dfrac{2}{3}\right)=2\dfrac{5}{6}\)
\(\left(\dfrac{1}{2}x+\dfrac{21}{2}\right).\left(-\dfrac{2}{3}\right)=\dfrac{17}{6}\)
\(\dfrac{1}{2}x+\dfrac{21}{4}=-\dfrac{17}{4}\)
\(\dfrac{1}{2}x=-\dfrac{19}{2}\)
\(x=-19\)
\(\left(50\%.x+5\dfrac{1}{4}\right).\dfrac{-2}{3}=2\dfrac{5}{6}\)
\(\dfrac{1}{2}.x+\dfrac{21}{4}=\dfrac{17}{6}:\dfrac{-2}{3}\)
\(\dfrac{1}{2}.x+\dfrac{21}{4}=\dfrac{-17}{4}\)
\(\dfrac{1}{2}.x=\dfrac{-17}{4}-\dfrac{21}{4}\)
\(\dfrac{1}{2}.x=\dfrac{-19}{2}\)
\(x=\dfrac{-19}{2}:\dfrac{1}{2}\)
\(x=-19\)
Tìm x biết x - \(\dfrac{3}{5}\) = \(\dfrac{2}{7}\) + \(\dfrac{1}{6}\)
\(x-\dfrac{3}{5}=\dfrac{2}{7}+\dfrac{1}{6}\)
\(\Leftrightarrow x-\dfrac{3}{5}=\dfrac{19}{42}\)
\(\Leftrightarrow x=\dfrac{19}{42}+\dfrac{3}{5}\)
\(\Leftrightarrow x=\dfrac{221}{210}\)
=>x-3/5=12/42+7/42=19/42
=>x=19/42+3/5=95/210+126/210=221/210
x-3/5=2/7+1/6
x-3/5=12/42+7/42
x-3/5=19/42
x=19/42+3/5
x=95/210 + 126/210
x=221/210
a) Tìm tập hợp các số nguyên x, biết rằng\(4\dfrac{5}{9}:2\dfrac{5}{18}-7< x< \left(3\dfrac{1}{5}:3,2+4,5.1\dfrac{31}{45}\right):\left(-21\dfrac{1}{2}\right)\)
b) tìm x, biết \(\left|x+\dfrac{1}{2}\right|+\left|x+\dfrac{1}{6}\right|+\left|x+\dfrac{1}{12}\right|+\left|x+\dfrac{1}{20}\right|+....+\left|x+\dfrac{1}{110}\right|-11x\)
c)Tính gt biểu thức \(C=2x^3-5y^3+2015\) tại x,y thỏa mãn \(\left|x-1\right|+\left(y+2\right)^{20}=0\)
Tìm x, biết
\(\left|x\right|-\dfrac{5}{6}.x=\dfrac{4}{9}.\dfrac{15}{8}\)
\(TH1:x\ge0\)
\(\Rightarrow x\left(1-\dfrac{5}{6}\right)=\dfrac{4}{9}.\dfrac{15}{8}\)
\(\Rightarrow x=\dfrac{\dfrac{4}{9}.\dfrac{15}{8}}{1-\dfrac{5}{6}}=5\left(TM\right)\)
\(TH2:x< 0\)
\(\Rightarrow x\left(-1-\dfrac{5}{6}\right)=\dfrac{4}{9}.\dfrac{15}{8}\)
\(\Rightarrow x=\dfrac{\dfrac{4}{9}.\dfrac{15}{8}}{-1-\dfrac{5}{6}}=-\dfrac{5}{11}\left(TM\right)\)
Vậy ...
Giải:
\(\left|x\right|-\dfrac{5}{6}.x=\dfrac{4}{9}.\dfrac{15}{8}\)
\(TH1:x\ge0\)
\(\left|x\right|-\dfrac{5}{6}.x=\dfrac{4}{9}.\dfrac{15}{8}\)
\(x-\dfrac{5}{6}.x=\dfrac{5}{6}\)
\(x.\left(1-\dfrac{5}{6}\right)=\dfrac{5}{6}\)
\(x.\dfrac{1}{6}=\dfrac{5}{6}\)
\(x=\dfrac{5}{6}:\dfrac{1}{6}\)
\(x=5\)
\(TH2:x\le0\)
\(\left|x\right|-\dfrac{5}{6}.x=\dfrac{4}{9}.\dfrac{15}{8}\)
\(-x-\dfrac{5}{6}.x=\dfrac{5}{6}\)
\(x.\left(-1-\dfrac{5}{6}\right)=\dfrac{5}{6}\)
\(x.\dfrac{-11}{6}=\dfrac{5}{6}\)
\(x=\dfrac{5}{6}:\dfrac{-11}{6}\)
\(x=\dfrac{-5}{11}\)
Vậy \(x\in\left\{\dfrac{-5}{11};5\right\}\)
Tìm x biết: (x-\(\dfrac{2}{3}\))\(^2\)=\(\dfrac{5}{6}\)
(\(x\)-\(\dfrac{2}{3}\))2\(=\)\(\dfrac{5}{6}\)
\(x\)-\(\dfrac{4}{9}\)\(=\)\(\dfrac{5}{6}\)
\(x\)\(=\)\(\dfrac{5}{6}\)+\(\dfrac{4}{9}\)
\(x\)\(=\)\(\dfrac{23}{18}\)
\(\left(x-\dfrac{2}{3}\right)^2=\dfrac{5}{6}\)
\(< =>\left(x-\dfrac{2}{3}\right)^2-\dfrac{5}{6}=0\)
<=>\(\left(x-\dfrac{2}{3}\right)^2-\left(\dfrac{\sqrt{5}}{\sqrt{6}}\right)^2=0\)
\(< =>\left(x-\dfrac{2}{3}+\dfrac{\sqrt{5}}{\sqrt{6}}\right)\left(x-\dfrac{2}{3}-\dfrac{\sqrt{5}}{\sqrt{6}}\right)=0\)
=>\(\left[{}\begin{matrix}x-\dfrac{2}{3}+\dfrac{\sqrt{5}}{\sqrt{6}}=0\\x-\dfrac{2}{3}-\dfrac{\sqrt{5}}{\sqrt{6}}=0\end{matrix}\right.< =>\left[{}\begin{matrix}x=\dfrac{2}{3}-\dfrac{\sqrt{5}}{\sqrt{6}}\\x=\dfrac{2}{3}+\dfrac{\sqrt{5}}{\sqrt{6}}\end{matrix}\right.\)
<=>\(\left[{}\begin{matrix}x=\dfrac{4-\sqrt{30}}{6}\\x=\dfrac{4+\sqrt{30}}{6}\end{matrix}\right.\)
VẬy..
Tìm số nguyên x , y biết : \(\dfrac{1}{x}+\dfrac{y}{3}=\dfrac{5}{6}\)
Tìm x,y ϵ Z biết: \(\dfrac{5}{x}\)- \(\dfrac{y}{3}\)= \(\dfrac{1}{6}\)
Lời giải:
$\frac{5}{x}-\frac{y}{3}=\frac{1}{6}$
$\Rightarrow \frac{15-xy}{3x}=\frac{1}{6}$
$\Rightarrow \frac{2(15-xy)}{6x}=\frac{x}{6x}$
$\Rightarrow 2(15-xy)=x$
$\Rightarrow 30=2xy+x$
$\Rightarrow 30=x(2y+1)$
$\Rightarrow x=\frac{30}{2y+1}$
Vì $x$ nguyên nên $\frac{30}{2y+1}$ nguyên
$\Rightarrow 2y+1$ là ước của $30$
Vì $2y+1$ lẻ nên $2y+1\in\left\{\pm 1; \pm 3; \pm 5; \pm 15\right\}$
$\Rightarrow y\in\left\{-1; 0; -2; 1; -3; 2; -8; 7\right\}$
Tương ứng với các giá trị $y$ trên ta có: $x\in\left\{-30; 30; -10; 10; -6; 6; -2;2\right\}$
Tìm x biết: x - 1 = \(\dfrac{6}{7}\) + \(\dfrac{1}{7}\) x\(\dfrac{2}{7}\) + \(\dfrac{1}{7}\) x \(\dfrac{5}{7}\)
\(\Rightarrow x-1=\dfrac{6}{7}+\dfrac{1}{7}\times\left(\dfrac{2}{7}+\dfrac{5}{7}\right)=\dfrac{6}{7}+\dfrac{1}{7}\times1\\ \Rightarrow x-1=\dfrac{6}{7}+\dfrac{1}{7}=1\\ \Rightarrow x=1+1=2\)
tìm x biết : \(x-\left(\dfrac{5}{6}-x\right)=x-\dfrac{2}{3}\)
`x-(5/6-x)=x-2/3`
⇒`x-5/6+x=x-2/3`
⇒`2x-5/6=x-2/3`
⇒`2x-5/6-x+2/3=0`
⇒`x-1/6=0`
⇒`x=1/6`