4 ^(n + 4) = 4^(n+2+2) = 4^2 {4^ (n+2)}
so
4^(n+4) - 4^(n+2) = 4^2 {4^ (n+2)} - 4^ (n+2) = 960........................i
facting out 4^ (n+2) eqn i becomes
4^ (n+2) [(4^2)-1] = 4^ (n+2)[16-1] = 4^ (n+2) [15] = 960................ii
dividing by 15 both sides of eqn ii
4^ (n+2) = 64 but 64 = 4^3, so
4^ (n+2) = 4^3, which makes
n+2 = 3, giving
n = 1