What is the co-efficient of x⁸ in the expression (x-1)(x-2).....(x-10)?

co-efficient of x^10 will be 1
co-efficient of x^9 will be sum of roots
co-efficient of x^8 will be sum of roots taken 2 at a time

hence ans= 1.2 +2.3+3.4 +...........+ 9.10

Now you can find this summation by using concepts of Seq and series