\(\dfrac{x}{5}=\dfrac{3}{y}\)Tìm số nguyên x biết

tính tổng: Q=\(\dfrac{5}{18\cdot21}+\dfrac{5}{21\cdot24}+\dfrac{5}{24\cdot27}+...+\dfrac{5}{123\cdot126}\)

A=\(\dfrac{1+\dfrac{1}{3}+\dfrac{1}{5}+\dfrac{1}{7}+...+\dfrac{1}{97}+\dfrac{1}{99}}{\dfrac{1}{1\times99}+\dfrac{1}{3\times97}+\dfrac{1}{5\times95}+...+\dfrac{1}{97\times3}+\dfrac{1}{99\times1}}\)

Tìm số nguyên n để A=\(\dfrac{n+1}{n-2}\)có giá trị nguyên, với n\(\ne\)2

5^2x-3-2.2^5=5^2.3

5^2x-3-2^5.2=5^2.3