Interpret basic exponential functions

**What is the initial value $a$ of the exponential function $g(n)=-\dfrac{81}{16}\cdot\left(\dfrac{2}{3}\right)^n\ $**? $a=$ [[☃ numeric-input 1]] **For which value of $n$ does $g(n)=-1\ $**? $n=$ [[☃ numeric-input 2]]