Đáp án:
Giải thích các bước giải:
Bài 2:
$\dfrac{a-1}{2}=\dfrac{b-2}{3}=\dfrac{c-3}{4}\\
=\dfrac{2a-2}{4}=\dfrac{3b-6}{9}=\dfrac{-c+3}{-4}=\dfrac{2a-2+3b-6-c+3}{4+9-4}=\dfrac{2a+3b-c-5}{1}=90\\
\rightarrow a=181 \quad b=272\quad c=363$
Câu 1:
$2x=3y=5z=k \rightarrow x=\dfrac{k}{2} \quad y=\dfrac{k}{3} \quad z=\dfrac{k}{5}\\
\rightarrow x-y+z=\dfrac{11}{30}.k=-33\Rightarrow k=-90\\
\rightarrow x=-45\quad y=-30 \quad z=-18$
Câu 2:
$\dfrac{x-1}{2}=\dfrac{y+3}{4}=\dfrac{z-5}{6}=k\\
\rightarrow x=2k+1 \quad y=4k-3\quad z=6k+5\\
\rightarrow 5z-3x-4y=8k+34=50\rightarrow k=2\\
\rightarrow x=5\quad y=5 \quad z=17$
Câu 3:
$\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}=k\\
\rightarrow x=2k \quad y=3k \quad z=4k\\
\rightarrow xyz=24k^{3}=648\rightarrow k=3\\
\rightarrow x=6\quad y=9 \quad z=12$
