Question

\(\dfrac{x}{3}=\dfrac{y}{-2}=\dfrac{z}{4}\) và 4x + y - 2z = -18

Answer 1

`-> x/3 = y/-2 = z/4 = (4x+y-2z)/(12 - 2 - 8) = -18/2 = -9`

`x/3 = -9 -> x = -27`

`y/-2 = - 9 -> y = 18`

`z/4 = -9 => z = -36`

Answer 2

Có: \(\dfrac{x}{3}=\dfrac{y}{-2}=\dfrac{z}{4}\Rightarrow\dfrac{4x}{12}=\dfrac{y}{-2}=\dfrac{2z}{8}\)

Áp dụng t/c dãy tỉ số bằng nhau, có: \(\dfrac{4x}{12}=\dfrac{y}{-2}=\dfrac{2z}{8}=\dfrac{4x+y-2z}{12-2-8}=-\dfrac{18}{2}=-9\)

\(\Rightarrow\left\{{}\begin{matrix}\dfrac{x}{3}=-9\\\dfrac{y}{-2}=-9\\\dfrac{z}{4}=-9\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}x=-27\\y=18\\z=-36\end{matrix}\right.\)