Question

Tìm số nguyên x và y
a) \(\dfrac{x}{2} +\dfrac{y}{3} = \dfrac{x+y}{2+3}\)
b) \(\dfrac{x}{3} - \dfrac{4}{y} = \dfrac{1}{5}\)

Answer 1

a) \(\dfrac{x}{2}+\dfrac{y}{3}=\dfrac{x+y}{2+3}\)

\(\dfrac{x}{2}=\dfrac{x+y}{2+3}-\dfrac{y}{3}\)

\(\dfrac{x}{2}=\dfrac{x+y}{5}-\dfrac{y}{3}\)

\(\dfrac{x}{2}=\dfrac{3\left(x+y\right)}{15}-\dfrac{5y}{15}\)

\(\dfrac{x}{2}=\dfrac{3x-2y}{15}\)

\(\Rightarrow15x=2\left(3x-2y\right)\)

\(15x=6x-4y\)

\(15x-6x=4y\)

\(9x=4y\)

(CÒN LẠI MÌNH KHÔNG BIẾT LÀM)

b) \(\dfrac{x}{3}-\dfrac{4}{y}=\dfrac{1}{5}\)

\(\dfrac{x}{3}=\dfrac{1}{5}+\dfrac{4}{y}\\ \)

\(\dfrac{x}{3}=\dfrac{1}{5}+\dfrac{20}{5y}\)

\(\dfrac{x}{3}=\dfrac{1+4}{y+1}\)

\(\Rightarrow x\left(y+1\right)=15\)

(CÒN NHIÊU TỰ LÀM NHÉ)