Question:
Approximate log base b of x, log_b(x).
Of course x can't be negative, and b > 1.
Answer:
f(x) = (-1/x + 1) / (-1/b + 1)
Step-by-step explanation:
log(1) is zero for any base.
log is strictly increasing.
log_b(b) = 1
As x descends to zero, log(x) diverges to -infinity
Graph of f(x) = (-1/x + 1)/a is reminiscent of log(x), with f(1) = 0.
Find a such that f(b) = 1
1 = f(b) = (-1/b + 1)/a
a = (-1/b + 1)
Substitute for a:
f(x) = (-1/x + 1) / (-1/b + 1)
f(1) = 0
f(b) = (-1/b + 1) / (-1/b + 1) = 1
