Explanation:
it grows exponentially.
a negative exponent like
n^-a
means only
1/(n^a)
-3 1/3³ = 1/27
-2 1/3² = 1/9
-1 1/3¹ = 1/3
0 3⁰ = 1
1 3¹ = 3
2 3² = 9
3 3³ = 27
so, 3^x comes from very small but positive values, and grows very fast (much faster than x itself and with ever increasing speed hence "exponentially") to very large and still positive numbers.