Question

Answer 1

\(\dfrac{5}{x-3}=\dfrac{x+4}{12}\)

\(\Leftrightarrow x^2+x-72=0\)

\(\Leftrightarrow\left(x+9\right)\left(x-8\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=8\end{matrix}\right.\)

Answer 2

\(\dfrac{5}{x-3}=\dfrac{x+4}{12}\)

\(\Rightarrow\left(x-3\right)\left(x+4\right)=5.12\)

\(\Rightarrow x^2+x-72=0\)

\(\Rightarrow\left(x-8\right)\left(x+9\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=8\\x=-9\end{matrix}\right.\)

Answer 3

\(\dfrac{5}{x-3}=\dfrac{x+4}{12}\)

<=> 5.12 = (x - 3)(x + 4)

<=> 60 = x² + 4x - 3x - 12 

<=> x² + x = -48 (Vô lí)

<=> x vô nghiệm

Answer 4

\(\dfrac{5}{x-3}=\dfrac{x+4}{12}\)

\(\Rightarrow\left(x-3\right)\left(x+4\right)=5.12\)

\(\Rightarrow x^2+x-12=60\)

\(\Rightarrow x^2+x-72=0\)

\(\Rightarrow x^2+9x-8x-72=0\)

\(\Rightarrow x\left(x+9\right)-8\left(x+9\right)=0\)

\(\Rightarrow\left(x+9\right)\left(x-8\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x+9=0\\x-8=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=-9\\x=8\end{matrix}\right.\)