Question

Tìm x,y,z,biết : \(\frac{x}{12}=\frac{y}{15}=\frac{z}{5}\)và x.y.z=20

Answer 1

Giải :

Đặt \(\frac{x}{12}=\frac{y}{15}=\frac{z}{5}=a\) 

\(\Rightarrow x=12.a\)

\(y=15.a\)

\(z=5.a\)

Thay vào x.y.z = 20

12.a.15.a.5.a = 20

( 12.15.5 ) . ( a.a.a ) = 20

900. a³ = 20

a³ = 20 ÷ 900

a³ = \(\frac{1}{45}\)

Đến đây bí ^^

Cbht

Answer 2

\(\frac{x}{12}=\frac{y}{15}=\frac{z}{5}=\frac{x.y.z}{12.15.5}=\frac{20}{900}=\frac{1}{45}\)

\(\frac{x}{12}\)=\(\frac{1}{45}\)=> x=\(\frac{1}{45}\).12=\(\frac{4}{15}\)

\(\frac{y}{15}=\frac{1}{45}=>y=\frac{1}{45}.15=\frac{1}{3}\)

\(\frac{z}{5}=\frac{1}{45}\)=> z = \(\frac{1}{45}.5=\frac{1}{9}\)