Explanation:
21^1 = 21 < 30
21^2 = 21² = 441 > 30
30 lies between 21^1 and 21^2.
21^x is a continuous function, so the value of x that makes 21^x = 30 must lie between 1 and 2, according to the intermediate value theorem.
_____
Using a calculator, we find x ≈ 1.117153.
