The sum of the coefficients in the expansion of ${(1+5\mathrm{x}-7{\mathrm{x}}^3)}^{3165}$ is

Putting $\mathrm{x}=1 \text{in}{ (1+5\mathrm{x}-7{\mathrm{x}}^3)}^{3165}$, the required sum of 
coefficients = (1 + 5 – 7)³¹⁶⁵ = (– 1)³¹⁶⁵ = –1.