Bạn tham khảo!
$\dfrac{x}{10}$ $=$ $\dfrac{y}{5}$ $;$ $\dfrac{y}{2}$ $=$ $\dfrac{z}{5}$ và $2x$ $-$ $3y$ $+$ $4z$ $=$ $330$
Ta có : $\dfrac{x}{10}$ $=$ $\dfrac{y}{5}$
$→$ $\dfrac{x}{20}$ $=$ $\dfrac{y}{10}$ (1)
Ta có : $\dfrac{y}{2}$ $=$ $\dfrac{z}{5}$
$→$ $\dfrac{y}{10}$ $=$ $\dfrac{z}{25}$ (2)
Từ (1) và (2) $→$ $\dfrac{x}{20}$ $=$ $\dfrac{y}{10}$ $=$ $\dfrac{z}{25}$
$→$ $\dfrac{2x}{40}$ $=$ $\dfrac{3y}{30}$ $=$ $\dfrac{4z}{100}$
Áp dụng t/c dãy tỉ số $=$ nhau ta có :
$\dfrac{2x}{40}$ $=$ $\dfrac{3y}{30}$ $=$ $\dfrac{4z}{100}$ $=$ $\dfrac{2x-3y+4z}{40-30+100}$ $=$ $\dfrac{330}{110}$ $=$ $3$
$→$ $\dfrac{2x}{40}$ $=$ $3$ $→$ $2x$ $=$ $120$ $→$ $x$ $=$ $60$
và $\dfrac{3y}{30}$ $=$ $3$ $→$ $3y$ $=$ $90$ $→$ $y$ $=$ $30$
và $\dfrac{4z}{100}$ $=$ $3$ $→$ $4z$ $=$ $300$ $→$ $z$ $=$ $75$
$FbBinhne2k88$
