{n \choose 0}\cdot{n \choose n}x^n+{n \choose 1}x\cdot{n \choose n-1}x^{n-1}+{n \choose 2}x^2\cdot{n \choose n-2}x^{n-2}+{n \choose 3}x^3\cdot{n \choose n-3}x^{n-3}+...+{n \choose n}x^{n}\cdot{n \choose 0}x^{0}