If the coefficient of x^{12} in the expansion of (x^3 + 1)^m is 210,then the coefficient of x^{15} is

Answer 1

if m=10, then ₁₀C₆(x³)⁴(1)⁶ = 210x¹² so,

₁₀C₅(x³)⁵(1)⁵ = 252x¹⁵