Question

Tìm x , biết : \(\dfrac{1+2y}{18}=\dfrac{1+4y}{24}=\dfrac{1+6y}{6x}\)

Answer 1

\(\dfrac{1+2y}{18}=\dfrac{1+4y}{24}\Rightarrow\dfrac{2+4y}{36}=\dfrac{1+4y}{24}\)

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\dfrac{1+6y}{6x}=\dfrac{2+4y}{36}=\dfrac{1+4y}{24}=\dfrac{\left(2+4y\right)-\left(1+4y\right)}{36-24}=\dfrac{1}{12}\)

\(\Rightarrow y=\dfrac{\dfrac{1}{12}.24-1}{4}=\dfrac{1}{4}=0,25\)

\(\Rightarrow\dfrac{1+6y}{6x}=\dfrac{1+1,5}{6x}\)

\(\Rightarrow\dfrac{2,5}{6x}=\dfrac{1}{12}\)

\(\Rightarrow6x=2,5:\dfrac{1}{12}=30\Leftrightarrow x=5\)

Vậy x = 5