Question

tim x,y,z la cac so nguyen

a) x-y=0,y+2z=1

b) x+y+z=7

Answer 1

                          Giải

Ta có : \(y+2z=1\)

\(\Leftrightarrow2z=1-y\)

\(\Rightarrow z=\frac{1-y}{2}\)

Vì \(x-y=0\) nên \(x=y\)

Ta có :\(x+y+z=7\)

\(\Rightarrow2y+\frac{1-y}{2}=7\)

\(\Rightarrow\frac{4y}{2}+\frac{1-y}{2}=7\)

\(\Rightarrow\frac{4y+1-y}{2}=7\)

\(\Leftrightarrow4y+1-y=7\times2\)

\(\Leftrightarrow3y+1=14\)

\(\Leftrightarrow3y=14-1\)

\(\Leftrightarrow3y=13\)

\(\Leftrightarrow y=\frac{13}{3}\)

\(\Leftrightarrow x=\frac{13}{3}\)

\(\Leftrightarrow z=7-\frac{13}{3}.2=\frac{-5}{3}\)

Mà x , y ,z là số nguyên nên không có x , y , z cần tìm