Question

tìm x , y , z 

x : y : z = 3 : 4 : 5 và 4x - 3y + 4z = 36

Answer 1

Cái chỗ mà x/3 = y/4= z/5= 4x/12-3y/12+4z/20 =36/20=9/5

Sau đó tìm x;y;z

Answer 2

\(x:y:z=3:4:5\Leftrightarrow x=3k;y=4k;z=5k.\)

\(\Rightarrow4x-3y+4z=12k-12k+20k=36\Leftrightarrow20k=36\Leftrightarrow k=\frac{9}{5}\)

\(\Rightarrow x=\frac{27}{5};y=\frac{36}{5};z=9\)