Bài 1:
1:
a: \(\dfrac{-45}{56}< >\dfrac{-55}{67}\)
b: \(\dfrac{-4}{5}=\dfrac{144}{-180}\)
2:
a: \(\dfrac{5}{x}=\dfrac{15}{20}=\dfrac{3}{4}\)
nên x=20/3
b: \(\dfrac{x}{-3}=\dfrac{-27}{x}\)
nên \(x^2=81\)
hay \(x\in\left\{9;-9\right\}\)
c: \(\dfrac{4}{3y-1}=\dfrac{2}{25}\)
nên 3y-1=50
=>3y=51
hay y=17