Question

Tìm x biết:

a,\(\dfrac{x+1}{x-2}=\dfrac{3}{4}\)

\(b,\dfrac{2x-3}{x+1}=\dfrac{4}{7}\)

\(c,\dfrac{2x+4}{7}=\dfrac{4x-2}{15}\)

Answer 1

a . \(\dfrac{x+1}{x-2}=\dfrac{3}{4}\)

=> \(\left(x+1\right).4=3.\left(x-2\right)\)

=> \(4x+4=3x-6\)

=> \(4x-3x=-6-4\)

=> x = -10

b. \(\dfrac{2x-3}{x+1}=\dfrac{4}{7}\)

=> \(\left(2x-3\right).7=4.\left(x+1\right)\)

=> \(14x-21=4x+4\)

=> \(14x-4x=4+21\)

=> \(10x=25\)

=> \(x=\dfrac{5}{2}\)

c. \(\dfrac{2x+4}{7}=\dfrac{4x-2}{15}\)

=> \(\left(2x+4\right).15=\left(4x-2\right).7\)

=> \(30x+60=28x-14\)

=> \(30x-28x=-14-60\)

=> \(2x=-74\)

=> \(x=-37\)

#Yiin

Answer 2

a, \(\dfrac{x+1}{x-2}=\dfrac{3}{4}\Rightarrow4\left(x+1\right)=3\left(x-2\right)\)

\(\Rightarrow4x+4=3x-6\)

\(\Rightarrow4x-3x=-6-4\Rightarrow x=-10\)

b, \(\dfrac{2x-3}{x+1}=\dfrac{4}{7}\Rightarrow7\left(2x-3\right)=4\left(x+1\right)\)

\(\Rightarrow14x-21=4x+4\)

\(\Rightarrow14x-4x=4+21\Rightarrow10x=25\Rightarrow x=\dfrac{5}{2}\)

c, \(\dfrac{2x+4}{7}=\dfrac{4x-2}{15}\Rightarrow15\left(2x+4\right)=7\left(4x-2\right)\)

\(\Rightarrow30x+60=28x-14\)

\(\Rightarrow30x-28x=-14-60\)

\(\Rightarrow2x=-74\Rightarrow x=-37\)