Question

tìm x trong các tỉ lệ thức sau :
a) \(\frac{37-x}{x+13}=\frac{3}{7}\)

b)\(\frac{x+4}{20}=\frac{5}{x+4}\)

Answer 1

\(\text{a)}\frac{37-x}{x+13}=\frac{3}{7}\)

\(\Leftrightarrow3\left(x+13\right)=7\left(37-x\right)\)

\(\Leftrightarrow3x+39=259-7x\)

\(\Leftrightarrow3x+7x=259-39\)

\(\Leftrightarrow10x=220\)

\(\Leftrightarrow x=22\)

Answer 2

\(\text{b)}\frac{x+4}{20}=\frac{5}{x+4}\)

\(\Leftrightarrow\left(x+4\right)^2=100\)

\(\Leftrightarrow\orbr{\begin{cases}x+4=10\\x+4=-10\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=6\\x=-14\end{cases}}\)

Answer 3

tìm x trong tỉ lệ thức sau x/64=-3/0.8;20/17=x/81