Fill in the blanks. a. The $(r+1)$ st term of the expansion of $(a+b)^{n}$ is $\frac{n !}{r !(n-\quad) !} a^{-r} b$ b. To use the specific term formula to find the 6th term of the expansion of $\left(m+\frac{x}{2}\right)^{8},$ we note that $r=, n=, a=$ and $b=$