Question

An exponential function, f(x), passes through the points (2,5) and (8,20). Determine the value of f(25) to the nearest integer.

Answer 1

assume: f(x) = A(bx); then: f(8) = A(b8) = 20;

and: f(2) = A(b2) = 5

dividing the first equation by the second equation gives: b6 = 4; or: b = 4(1/6) = 1.26;

then: A(1.262) = 5; or: A = 5/(1.262) = 3.15; then: f(x) = 3.15(1.26x);

so that: f(25) = 3.15(1.2625) = 1017.6 ---> 1018

Explanation:

hope it helps and Work..