Question

a,\(\dfrac{x}{-4}=\dfrac{-9}{x}\)
b,\(\dfrac{x-1}{-15}=\dfrac{-60}{x-1}\)
c,\(\dfrac{2x+1}{5}=\dfrac{3y-2}{7}=\dfrac{2x+3y-1}{6x}\)
d,\(\dfrac{x-2}{x-1}=\dfrac{x+4}{x+7}\)
Ai tìm x giúp mình với!!Mình sẽ tích điểm cho!!

Answer 1

Giải:

a) \(\dfrac{x}{-4}=\dfrac{-9}{x}\)

\(\Leftrightarrow x.x=-4.\left(-9\right)\)

\(\Leftrightarrow x^2=36\)

\(\Leftrightarrow x=\pm6\)

Vậy ...

b) \(\dfrac{x-1}{-15}=\dfrac{-60}{x-1}\)

\(\Leftrightarrow\left(x-1\right)^2=900\)

\(\Leftrightarrow\left[{}\begin{matrix}x-1=30\\x-1=-30\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=31\\x=-29\end{matrix}\right.\)

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d) \(\dfrac{x-2}{x-1}=\dfrac{x+4}{x+7}\)

\(\Leftrightarrow\left(x-2\right)\left(x+7\right)=\left(x-1\right)\left(x+4\right)\)

\(\Leftrightarrow x^2+5x-14=x^2+3x-4\)

\(\Leftrightarrow5x-14=3x-4\)

\(\Leftrightarrow2x=10\)

\(\Leftrightarrow x=5\)

Vậy ...