\(\text{Áp dụng nhị thức Newton ta có:}\\\left(x+\dfrac{1}{x}\right)^5\\=C_5^0x^5+C_5^1x^4.\dfrac{1}{x}+C_5^2x^3\left(\dfrac{1}{x}\right)^2+C_5^3x^2\left(\dfrac{1}{x}\right)^3+C_5^4x\left(\dfrac{1}{x}\right)^4+C_5^5\left(\dfrac{1}{x}\right)^5\\=x^5+5x^3+10x+\dfrac{10}{x}+\dfrac{5}{x^3}+\dfrac{1}{x^5}.\)
