Question

Tìm x trong tỉ lệ thức 

a) x-3/5-x=5/7

b)x-2/ x-1=x+4/x+7

Answer 1

\(a,\frac{x-3}{5-x}=\frac{5}{7}\)

\(\Rightarrow\left(x-3\right).7=5\left(5-x\right)\)

\(\Rightarrow7x-21=25-5x\)

\(\Rightarrow12x=46\)

\(\Rightarrow x=\frac{23}{6}\)

\(b,\frac{x-2}{x-1}=\frac{x+4}{x+7}\)

\(\Rightarrow\left(x-2\right)\left(x+7\right)=\left(x+4\right)\left(x-1\right)\)

\(\Rightarrow x^2+7x-2x-14=x^2-x+4x-4\)

\(\Rightarrow x^2+5x-14=x^2+3x-4\)

\(\Rightarrow x^2+5x-x^2-3x=14-4\)

\(\Rightarrow2x=10\)

\(\Rightarrow x=5\)