Answer:
y = 10(½)^(x)
Step-by-step explanation:
In writing exponential functions passing through points, we will just substitute the x and y values in each case into y = ab^(x).
Now, for point (-1, 20), the exponential function is; 20 = ab^(-1)
20 = a/b
For the point (1, 5), the exponential function is; 5 = ab^(1)
5 = ab
From 20 = a/b, we have; a = 20b
Thus, putting 20b for a in 5 = ab, we have;
5 = 20b(b)
b² = 5/20
b² = 1/4
b = √(1/4)
b = 1/2
Since a = 20b, then;
a = 20 × 1/2
a = 10
Thus, from y = ab^(x), we have;
y = 10(½)^(x)
