Binomial theorem

What is the coefficient of x¹⁰ in the expansion of (1-x² )²⁰ (2-x² -1/x²)^-5

If the 4^th term in the expansion of (mx+1/x)ⁿ is 5/2 , then what is the value of mn?

In a binomial expansion of (x + y)^{2n + 1}(x – y)^{2n + 1}, the sum of middle terms is zero. What is the value of x²/y²?

In the expansion of (1 + x)^p (1 + x)^q, if the coefficient of x³ is 35, then what is the value of (p + q)?