Question

Y=6*4^x for x=-3 =? ..........

Answer 1

Y = 6 * 4^x
y = 6 * 4^-3 
y = 6 * 0.015625
y = 0.09375

Answer 2

When you raise a coefficient/number to a negative power, you divide the number 1 by that coefficient and power, and make the power positive.

For example:
$3^{-2}$ = $\frac{1}{3^{2}}$

Vice versa:
$\frac{1}{3^{-2}}$ = $3^{2}$

With this in mind, plug in -3 for x.

$y~=~6~*~4^{-3}$
$y~=~6~*~ \frac{1}{4^{3}}$
$y~=~6~*~ \frac{1}{64}$
$y~=~ \frac{6}{64}$

$y~=~ \frac{3}{32}$ 
     or
y≈0.09735