Question

tim x va y biet

a) \(\frac{x}{y}=\frac{7}{3}\)và 5x-2y = 87

 

Answer 1

\(\frac{x}{y}=\frac{7}{3}\Rightarrow\frac{x}{7}=\frac{y}{3}\Rightarrow\frac{5x}{35}=\frac{2y}{6}=\frac{5x-2y}{35-6}=\frac{87}{29}=3\)

=> x/7 = 3 => x=21

y/3 = 3 => y=9

Answer 2

\(\frac{x}{y}=\frac{7}{3}=3x=7y=\frac{x}{7}=\frac{y}{3}\)

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

\(\frac{x}{7}=\frac{y}{3}=\frac{5x}{5.7}=\frac{2y}{2.3}=\frac{2x-2y}{35-6}=\frac{87}{29}=3\)

\(\frac{x}{7}=3\Rightarrow x=3.7=21\)

\(\frac{y}{3}=3\Rightarrow y=3.3=9\)

Vậy x=21 ; y=9

Answer 3

Ta có: \(\frac{x}{y}\)= \(\frac{7}{3}\)\(\Rightarrow\)\(\frac{x}{7}\)=\(\frac{y}{3}\)

Ta lại có: \(\frac{x}{7}\)=\(\frac{y}{3}\)=\(\frac{5x-2y}{5.7-2.3}\)=\(\frac{87}{29}=3\)

Từ đó tính x và y nha bn.

Answer 4

\(\frac{x}{y}=\frac{7}{3}\Rightarrow3x=7y\Rightarrow\frac{y}{3}=\frac{x}{7}\)

Ap dung cong thuc cua day ti so bang nhau , ta co : 

\(\frac{y}{3}=\frac{x}{7}=\frac{5x}{15}=\frac{2y}{14}=\frac{5x-2y}{15-14}=\frac{87}{1}=87\)

\(\Rightarrow\hept{\begin{cases}\frac{y}{3}=87\\\frac{x}{7}=87\end{cases}\Rightarrow\hept{\begin{cases}y=87.3=261\\x=87.7=609\end{cases}}}\)

Vay ....