Question

Tìm số nguyên x biết :

\(\dfrac{4}{x-1}\)=\(\dfrac{3}{15}\)

Answer 1

ĐKXĐ:\(x-1\ne0\Rightarrow x\ne1\)

\(\dfrac{4}{x-1}=\dfrac{3}{15}\\ \Leftrightarrow\dfrac{4}{x-1}=\dfrac{1}{5}\\ \Leftrightarrow x-1=5.4\\ \Leftrightarrow x-1=20\\ \Leftrightarrow x=21\)

Answer 2

\(\Leftrightarrow\left(x-1\right).3=15.4\)

\(\Leftrightarrow\left(x-1\right).3=60\)

\(\Leftrightarrow x-1=20\)

\(\Leftrightarrow x=21\)

 Vậy x = 21

Answer 3