Lời giải:
\(\frac{y-2}{5}=\frac{x+1}{3}=\frac{2z+14}{9}\)
\(\Leftrightarrow \frac{y-2}{5}=\frac{2x+2}{6}=\frac{2z+14}{9}=\frac{2x+2+2z+14}{6+9}\) (áp dụng tính chất dãy tỉ số bằng nhau)
\(\Leftrightarrow \frac{y-2}{5}=\frac{2(x+z)+16}{15}=\frac{2y+16}{15}\)
\(\Leftrightarrow 3(y-2)=2y+16\Leftrightarrow y=22\)
Thay vào giả thiết ban đầu:
\(\Rightarrow \frac{x+1}{3}=\frac{2z+14}{9}=\frac{22-2}{5}=4\)
\(\Rightarrow \left\{\begin{matrix} x+1=12\rightarrow x=11\\ 2z+14=36\rightarrow z=11\end{matrix}\right.\)
Vậy \((x,y,z)=(11,22,11)\)
Theo đề bài:\(x+z=y\Leftrightarrow x+z-y=0\Leftrightarrow2x+2z-2y=0\)
Ta có:
\(\dfrac{x+1}{3}=\dfrac{y-2}{5}=\dfrac{2z+14}{9}\Leftrightarrow\dfrac{2x+2}{6}=\dfrac{2y-4}{10}=\dfrac{2z+14}{9}=\dfrac{2x+2-2y+4+2z+14}{6-10+9}=\dfrac{20}{5}=4\)
\(\Rightarrow\left\{{}\begin{matrix}\dfrac{x+1}{3}=4\Leftrightarrow x=3.4-1=11\\\dfrac{y-2}{5}=4\Leftrightarrow y=4.5+2=22\\\dfrac{2z+14}{9}=4\Leftrightarrow z=\dfrac{4.9-14}{2}=11\end{matrix}\right.\)
Suy đi tính lại vẫn ngắn hơn :V
