#### Answer

The first three terms are:
$a=1728
\\a_2=1296
\\a_3=972$

#### Work Step by Step

To find the first three terms, the value of the common ratio $r$ is needed.
Note that the previous term of a geometric sequence can be found by dividing the common ratio $r$ to the current term.
The geometric sequence has:
$r=0.75$
$a_4=729$
To find the third term, divide $a_4$ by the common ratio $r$ to obtain:
$a_3 = \dfrac{a_4}{r}
\\a_3=\dfrac{729}{0.75}
\\a_3=972$
To find the second term, divide $a_3$ by the common ratio $r$ to obtain:
$a_2 = \dfrac{a_3}{r}
\\a_2=\dfrac{972}{0.75}
\\a_2=1296$
To find the first term, divide $a_2$ by the common ratio $r$ to obtain:
$a = \dfrac{a_2}{r}
\\a=\dfrac{1296}{0.75}
\\a=1728$