The coefficient of $x^2$ in the expansion of $(1-3x)^{-1/4}$ is

The formula $(a + b)^m = a^m + ma^{m-1}b + \frac{m(m - 1)}{1 \cdot 2}a^{m - 2}b^2 + \dots$ holds when

$1 - \frac{3}{16} + \frac{1 \cdot 4}{1 \cdot 2} \left(\frac{3}{16}\right)^2 - \frac{1 \cdot 4 \cdot 7}{1 \cdot 2 \cdot 3} \left(\frac{3}{16}\right)^3 + \ldots$

If $y = \frac{3}{4} + \frac{3 \times 5}{4 \times 8} + \frac{3 \times 5 \times 7}{4 \times 8 \times 12} + \ldots$ to $\infty$,then

If $(a + bx)^{-2} = \frac{1}{4} - 3x + \dots$,then $(a, b) = $

In the expansion of $\frac{2x+1}{(1+x)(1-2x)}$,the sum of the coefficients of the first $5$ odd powers of $x$ is