Explanation:
common ratio is usually used for geometric sequences.
every term is created by multiplying the previous term by a certain constant factor (= common ratio).
this factor or common ratio is in our case 4.
such a sequence is a function f(x) for x being whole numbers.
a0 = 1
a1 = a0×4 = 1×4 = 4
a2 = a1×4 = 4×4 = 16
...
an = 4^n
as general function that is then
f(x) = 4^x
a horizontal shift right by 6 units means that now the functional value of x is the same as it was for (x-6) before the shift.
e.g. f_new(6) = f_old(0)
so, the function is
f(x) = 4^(x - 6) or (4^x)/4⁶