Question

ai giúp mình đi

x/-3=y/7;y/-2=z/5 và -2x-4y+5z=146

Answer 1

Vì \(\dfrac{x}{-3}=\dfrac{y}{7};\dfrac{y}{-2}=\dfrac{z}{5}\)

\(\Rightarrow\dfrac{x}{-3}=\dfrac{y}{7};\dfrac{y}{5}=\dfrac{z}{-2}\)

\(\Rightarrow\dfrac{x}{-15}=\dfrac{y}{35};\dfrac{y}{35}=\dfrac{z}{-14}\)

\(\Rightarrow\dfrac{x}{-15}=\dfrac{y}{35}=\dfrac{z}{-14}\)

\(\Rightarrow\dfrac{-2x}{30}=\dfrac{4y}{140}=\dfrac{5z}{-70}\)

Áp dụng tính chất dãy tỉ số bằng nhau, ta có:

\(\dfrac{-2x}{30}=\dfrac{4y}{140}=\dfrac{5z}{-70}=\dfrac{-2x-4y+5z}{30-140-70}=\dfrac{146}{-180}=\dfrac{-73}{90}\)