Question

 Tim x,y,z biet:

a,   x/2=y/3; y/5=z/7 va x+y+z=138

b,    10x=15y=21z va 3x-7y+5z=30

 

 

Answer 1

Ta có : \(\frac{x}{2}=\frac{y}{3}\Rightarrow\frac{x}{10}=\frac{y}{15}\)

            \(\frac{y}{5}=\frac{z}{7}\Rightarrow\frac{y}{15}=\frac{z}{21}\)

Do đó : \(\frac{x}{10}=\frac{y}{15}=\frac{z}{21}\)

Ta có : \(\frac{x}{10}=\frac{y}{15}=\frac{z}{21}=\frac{x+y+z}{10+15+21}=\frac{138}{46}=3\)

Nên : \(\frac{x}{10}=3\Rightarrow x=30\)

           \(\frac{y}{15}=3\Rightarrow y=45\)

           \(\frac{z}{21}=3\Rightarrow z=63\)

Vậy x = 30 ; y = 45 ; z = 63