(i) Find the value of r, if the coefficients of (2r + 2)th and (r-2)th terms in the expansion of (1+x)^{18} are equal.
(ii) Find the coefficient of x−17 in the expansion of (x4−1x3)15
(iii) Find the term independent of x in the expansion of (2x−1x)10
(i) r = 6
(ii) -1365
(iii) x = - 8064