## the values of a, b and n

The 3rd , 4th and 5th terms in the expansion of (a + b)n are respectively 84, 280 and 560. Find the values of a, b and n.

The 3rd , 4th and 5th terms in the expansion of (a + b)n are respectively 84, 280 and 560. Find the values of a, b and n.

Find the value of r, if the coefficient of (2r + 4)th and (r – 2)th terms in the expansion of (1 + x)18 are equal.

Find ‘a’ if the 11th and 12th terms of the expansion (2 + a)40 are equal.