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a)\(\frac{x+7}{x}=\frac{4}{5}\)
=>5(x+7)=4x
5x+35=4x
5x-4x=-35
x=-35
Vậy x=-35
b)(x-20)/(x+40)=(x+70)/(x-10)
(x-20)*(x-10)=(x+40)*(x+70)
x(x-10)-20(x-10)=x(x+70)+40(x+70)
x2-10x-20x+200=x2+70x+40x+2800
x2-x2-10x-20x-70x-40x=2800-200
0-(10x+20x+70x+40x)=2600
-140x=2600
x=2600/(-140)
x=\(-\frac{130}{7}\)
Vậy x=-130/7
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a) (x + 15) : x = 4 : 3
=> x : x + 15 : x = \(\frac{4}{3}\)
=> 1 + 15 : x = \(\frac{4}{3}\)
=> 15 : x = \(\frac{4}{3}\)- 1 = \(\frac{1}{3}\)
=> x = 15 : \(\frac{1}{3}\)
=> x = 45
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\(\frac{x-20}{x-10}=\frac{x+40}{x+70}=\frac{-20-40}{-10-70}=\frac{6}{8}=\frac{3}{4}.\)
\(\Rightarrow4\cdot\left(x-20\right)=3\cdot\left(x-10\right)\Leftrightarrow4x-80=3x-30\Leftrightarrow x=50.\)
bn dinh thuy linh gioi that, toàn dung ngôn ngữ toán hoc nên bai lam rat ấn tuong
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\(a,\frac{x+15}{x}=\frac{4}{3}\Rightarrow4x=3x+45\Leftrightarrow x=45\)
\(b,\frac{7,5-x}{3,5+x}=\frac{5}{6}\Rightarrow17,5+5x=45-6x\Leftrightarrow11x=27,5\Rightarrow x=2,5\)
\(c,\frac{x-20}{x-10}=\frac{x+40}{x+70}\Rightarrow\left(x-20\right)\left(x+70\right)=\left(x-10\right)\left(x+40\right)\)
\(\Leftrightarrow x^2+50x-1400=x^2+30x-400\)
\(\Leftrightarrow20x=1000\)
\(\Rightarrow x=50\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a. \(\frac{\left(x+15\right)}{x}=\frac{4}{3}\Leftrightarrow4x=3\left(x+15\right)\Leftrightarrow4x=3x+45\Leftrightarrow x=45\)
Vậy x=45
b. \(\frac{7,5-x}{3,5+x}=\frac{5}{6}\Leftrightarrow5\left(3,5+x\right)=6\left(7,5-x\right)\Leftrightarrow17,5+5x=45-6x\Leftrightarrow11x=27,5\Leftrightarrow x=2,5\)
Vậy x=2,5
c. \(\frac{x+20}{x-10}=\frac{x+40}{x+70}\Leftrightarrow\left(x+40\right)\left(x-10\right)=\left(x+20\right)\left(x+70\right)\)
\(\Leftrightarrow x^2+30x-400=x^2+90x+1400\Leftrightarrow-60x=-30\Leftrightarrow x=-30\)
Vậy x=-30
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\left(x+15\right):x=4:3\)
=>\(1+\dfrac{15}{x}=\dfrac{4}{3}\)
=>\(\dfrac{15}{x}=\dfrac{1}{3}\)
=>\(x=3.15=45\)
Vậy x=45
b)\(\dfrac{7,5-x}{3,5+x}=\dfrac{5}{6}\)
\(6\left(7,5-x\right)=5\left(3,5+x\right)\)
=>\(45-6x=17,5+5x\)
=>\(-11x=-27,5\)
=>\(x=2,5\)
Vậy...
c)\(\dfrac{x-20}{x-10}=\dfrac{x+40}{x+70}\)
=>\(\left(x-20\right)\left(x+70\right)=\left(x-10\right)\left(x+40\right)\)
=>\(x^2+50x-140=x^2+30x-40\)
=>\(20x=100\)
=>\(x=50\)
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a, \(\left(7,5-x\right):\left(3,5+x\right)=5:6\)
\(\Leftrightarrow\frac{7,5-x}{3,5+x}=\frac{5}{6}\)
\(\Leftrightarrow6.\left(7,5-x\right)=5.\left(3,5+x\right)\)
\(\Leftrightarrow45-6x=17,5+5x\)
\(\Leftrightarrow45-17,5=5x+6x\)
\(\Leftrightarrow27,5=11x\)
\(\Leftrightarrow x=\frac{27,5}{11}=2,5\)
Vậy : \(x=2,5\)
b) Tương tự như câu a.
Chúc bạn học tốt nhé !!