[ 1/5 + 1/35 + 1/63 ] x [ x-2 ] =1
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M
1
PT
1
CM
12 tháng 1 2018
1/3x5+1/5x7+1/7x9)xX=1
1/2x(1/3-1/5+1/5-1/7+1/7-1/9)xX=1
1/2x(1/3-1/9)xX=1
1/2x2/9xX=1
1/9xX=1
X=9
PT
1
CM
3 tháng 5 2018
1/3x5+1/5x7+1/7x9)xX=11/2x(1/3-1/5+1/5-1/7+1/7-1/9)xX=11/2x(1/3-1/9)xX=11/2x2/9xX=11/9xX=1X=9
BM
2
LT
17 tháng 10 2017
\(\left(\frac{1}{5}+\frac{1}{35}+\frac{1}{63}\right)\cdot x=1\)
\(\frac{11}{45}\cdot x=1\)
\(x=\frac{45}{11}\)
17 tháng 10 2017
(1/5+1/35+1/63)*x=1
(441/2205+63/2205+35/2205)*x=1
11/45*x=1
x=1:11/45
x=45/11
30 tháng 10 2018
b) \(\left(x-3\right)^2+3x-22=\sqrt{x^2-3x+7}\)
\(\Leftrightarrow x^2-6x+9+3x-22=\sqrt{x^2-3x+7}\)
\(\Leftrightarrow\left(x^2-3x+7\right)-\sqrt{x^2-3x+7}-20=0\)
Đặt \(\sqrt{x^2-3x+7}=t\left(t\ge0\right)\left(1\right)\)
\(\Rightarrow t^2-t-20=0\)
\(\Rightarrow x_1=5\left(TM\right);x_2=-4\left(KTM\right)\)
Thay t=5 vào (1), ta có :
\(\sqrt{x^2-3x+7}=5\)
\(\Leftrightarrow x^2-3x+7=25\)
\(\Leftrightarrow x^2-3x-18=0\)
\(\Rightarrow x_1=6;x_2=-3\)
vậy...
TT
2
26 tháng 8 2020
\(\left(\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)×x=\frac{6}{5}\)
\(\frac{3}{55}×x=\frac{6}{5}\)
\(x=\frac{6}{5}:\frac{3}{55}\)
\(x=22\)
vậy \(x=22\)
VM
26 tháng 8 2020
\(\left(\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right).x=\frac{6}{5}\)
\(\Leftrightarrow\left(\frac{1.99}{35.99}+\frac{1.55}{63.55}+\frac{1.35}{99.35}\right).x=\frac{6}{5}\)
\(\Leftrightarrow\left(\frac{99}{3465}+\frac{55}{3465}+\frac{35}{3465}\right).x=\frac{6}{5}\)
\(\Leftrightarrow\left(\frac{99+55+35}{3465}\right).x=\frac{6}{5}\)
\(\Leftrightarrow\frac{189}{3465}.x=\frac{6}{5}\)
\(\Leftrightarrow\frac{3}{55}.x=\frac{6}{5}\)
\(\Leftrightarrow x=\frac{6}{5}:\frac{3}{55}\)
\(\Leftrightarrow x=\frac{6}{5}.\frac{55}{3}\)
\(\Leftrightarrow x=\frac{330}{15}\)
\(\Leftrightarrow x=22\)
Vậy \(x=22.\)
28 tháng 11 2022
\(\Leftrightarrow\dfrac{2}{\left(x+1\right)\left(x+3\right)}+\dfrac{2}{\left(x+3\right)\left(x+5\right)}+\dfrac{2}{\left(x+5\right)\left(x+7\right)}+\dfrac{2}{\left(x+7\right)\left(x+9\right)}=\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{1}{x+1}-\dfrac{1}{x+3}+\dfrac{1}{x+3}-\dfrac{1}{x+5}+\dfrac{1}{x+5}-\dfrac{1}{x+7}+\dfrac{1}{x+7}-\dfrac{1}{x+9}=\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{1}{x+1}-\dfrac{1}{x+9}=\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{x+9-x-1}{\left(x+1\right)\left(x+9\right)}=\dfrac{2}{5}\)
=>2(x+1)(x+9)=5*8=40
=>x^2+9x+9=20
=>x^2+9x-11=0
hay \(x=\dfrac{-9\pm5\sqrt{5}}{2}\)
=>x^2+9x
TN
28 tháng 11 2017
ĐK:\(x\ne-1;-3;-5;-7;-9\)
\(pt\Leftrightarrow\frac{2}{\left(x+1\right)\left(x+3\right)}+\frac{2}{\left(x+3\right)\left(x+5\right)}+\frac{2}{\left(x+5\right)\left(x+7\right)}+\frac{2}{\left(x+7\right)\left(x+9\right)}=\frac{2}{5}\)
\(\Leftrightarrow\frac{1}{x+1}-\frac{1}{x+3}+\frac{1}{x+3}-...-\frac{1}{x+9}=\frac{2}{5}\)
\(\Leftrightarrow\frac{1}{x+1}-\frac{1}{x+9}=\frac{2}{5}\)\(\Leftrightarrow\frac{8}{\left(x+1\right)\left(x+9\right)}=\frac{2}{5}\)
\(\Leftrightarrow2\left(x+1\right)\left(x+9\right)=40\)\(\Leftrightarrow x^2+10x-11=0\)
\(\Rightarrow\orbr{\begin{cases}x-1=0\\x+11=0\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x=1\\x=-11\end{cases}}\) (thoả)
Vậy....
[ 1/5 + 1/35 + 1/63 ] x [ x-2 ] =1
\(\frac{63+9+5}{315}x\left(x-2\right)=1\)
\(\frac{77}{315}x\left(x-2\right)=1\)
\(\frac{11}{45}x\left(x-2\right)=1\)
\(x-2=1:\frac{11}{45}=\frac{45}{11}\)
\(x=\frac{45}{11}+2=\frac{67}{11}\)
\(\left(\frac{1}{5}+\frac{1}{35}+\frac{1}{63}\right)\times\left(x-2\right)=1\)
\(\frac{11}{45}\times\left(x-2\right)=1\)
\(x-2=\frac{45}{11}\)
\(x=\frac{67}{11}\)