Answer:
B)
Step-by-step explanation:
exponential function given by:
[tex] \displaystyle f(x )= a \cdot{b}^{x} [/tex]
where:
- a is the y-intercept
- b can be any number
since the function crosses y-axis at (0,4) point
to find a we can consider (1,8) point it tells us when x is 1 then y is 8 thus:
[tex] \displaystyle 8= 4 \cdot{b}^{1} [/tex]
[tex] \displaystyle 8= 4 \cdot{b}^{} [/tex]
divide both sides by 4:
[tex] \displaystyle \boxed{b = 2}[/tex]
altogether substitute:
[tex] \displaystyle f(x)= 4 \cdot{2}^{x} [/tex]
hence our answer is B)
