Question

The coefficient of x in the expansion of (x+5)^3 is

Answer 1

Using identity :-
( a + b )³ = a³ + b³ + 3a²b + 3ab²

a = x and b = 5


( x + 5 )³ = x³ + 125 + 15x² + 15x

Here the coefficient of x is 15 !!