If the coefficients of


If the coefficients of $x^{3}$ and $x^{4}$ in the expansion of $\left(1+a x+b x^{2}\right)(1-2 x)^{18}$ in powers of $x$ are both zero, then $(\mathrm{a}, \mathrm{b})$ is equal to :-

  1. $\left(16, \frac{251}{3}\right)$

  2. $\left(14, \frac{251}{3}\right)$

  3. $\left(14, \frac{272}{3}\right)$

  4. $\left(16, \frac{272}{3}\right)$

Correct Option: , 4


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