Question

\(\frac{x+4}{7+y}=\frac{4}{7}\)và \(x+y=22\)

Tìm x,y

Answer 1

X,y = 11

Answer 2

\(\frac{x+4}{7+y}=\frac{4}{7}\Rightarrow\frac{x+4}{4}=\frac{7+y}{7}\)

Áp dụng tính chất dãy tỉ số bằng nhau 

\(\frac{x+4}{4}=\frac{7+y}{7}=\frac{x+y+4+7}{4+7}=\frac{22+11}{11}=\frac{33}{11}=3\)

\(\frac{x+4}{4}=3\Rightarrow x+4=3.4=12\Rightarrow x=8\)

\(\frac{7+y}{7}=3\Rightarrow7+y=3.7=21\Rightarrow y=14\)

Vậy\(\left(x,y\right)=\left(8,14\right)\)

Answer 3

\(\frac{x+4}{7+y}=\frac{4}{7}\)

\(\Rightarrow7\left(x+4\right)=4\left(7+y\right)\)

\(\Rightarrow7x+28=28+4y\)

Vì 28 = 28 \(\Rightarrow7x=4y\)

\(\Rightarrow\frac{x}{4}=\frac{y}{7}=\frac{x+y}{4+7}=\frac{22}{11}=2\)

\(\Rightarrow x=2.4=8\); \(y=2.7=14\)

Vậy \(x=8;y=14\)