bài 4
\(\dfrac{x}{5}=\dfrac{y}{9}=\dfrac{x-y}{5-9}=\dfrac{50}{-4}=-12,5\)
x=-12,5.5=-62,5
y=-12,5.9=-112,5
b)
\(\dfrac{x}{y}=\dfrac{7}{10}=>\dfrac{x}{7}=\dfrac{y}{10}=\dfrac{x-y}{7-10}=\dfrac{30}{-3}=-10\)
x=-10.7=-70
y=-10.10=-100
c)
\(\dfrac{x}{7}=\dfrac{y}{15}=\dfrac{x+y}{7+15}=\dfrac{44}{22}=2\)
x=14
y=30
d)
\(\dfrac{x}{8}=\dfrac{y}{10}=\dfrac{x+y}{8+10}=\dfrac{72}{18}=4\)
x=32
y=40
