SOLUTION: Write a power Function of the form y=ab^x whose graph passes through the given points: (4,3) (9,4.5)

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: Write a power Function of the form y=ab^x whose graph passes through the given points: (4,3) (9,4.5)      Log On


   



Question 134605: Write a power Function of the form y=ab^x whose graph passes through the given points: (4,3) (9,4.5)
Found 2 solutions by stanbon, vleith:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Write a power Function of the form y=ab^x whose graph passes through the given points: (4,3) (9,4.5)
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You need to find a and b.
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EQUATIONS:
Substitute to get:
9 = a*b^4.5
3 = a*b^3
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Divide the 2nd equation into the 1st to get:
3 = b^(3/2)
Raise both sides to the (2/3) power to get:
b = 3^(2/3)
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Subsitute to solve for "a":
3 = a^3
3 = a*3^2
a = 3/9 = 1/3
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EQUATION:
y = (1/3)*3^(2x/3)
or
y = (1/3)* (3^(2/3))^x
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Cheers,
Stan H.

Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
Use Logs
Given:y=ab%5Ex
Log%28y%29+=+Log%28a%29+%2B+xLog%28b%29
Log%28y%29+-+xLog%28b%29+=+Log%28a%29+
Sub in both sets of points. Since Log(a) is the same in both equations, we can set them equal to each other.
Log%283%29+-+4Log%28b%29+=+Log%284.5%29+-+9Log%28b%29
Log%283%29+-+Log%284.5%29+=+-5Log%28b%29
%280.477+-+0.653%29%2F-5+=+Lob%28b%29
0.035218+=+Log%28b%29
10%5E0.035218+=+b
1.0845+=+b
Now solve for a
3+=+a%2A%281.0845%29%5E4+
3%2F1.383+=a
Function is:
y+=+2.169+%2A+1.0845%5Ex+
Verify the function by plugging in the given points