Answer:
y = 3(2^x)
Explanation:
Put the given point values in the equation and solve for 'a' and 'b'.
3 = a(b^0) = a . . . . . for x=0, y=3
The y-intercept has given us the value of 'a'.
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The other point will tell us 'b'.
48 = a(b^4) = 3(b^4) . . . . . for x=4, y=48
16 = b^4 . . . . . . . . . . . . . . . divide by 3
2^4 = b^4 ⇒ b = 2
The exponential function is ...
y = 3(2^x)
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Additional comment
We can use roots to find b:
16^(1/4) = (b^4)^(1/4) = b
2 = b . . . . your calculator can do this, or √(√16) = 16^(1/4) = 2.