Tuesday 18 August 2015

`(2,24) , (3,144)` Write an exponential function `y=ab^x` whose graph passes through the given points.

The given two points of the exponential function are (2,24) and (3,144).


To determine the exponential function


`y=ab^x`


plug-in the given x and y values.


For the first point (2,24), the values of x and y are x=2, y=24. Plugging them, the exponential function becomes:


`24=ab^2`     (Let this be EQ1.)


For the second point (3,144), the values of x and y are x=3 and y=144. Plugging them, the function becomes:


`144=ab^3`    ...

The given two points of the exponential function are (2,24) and (3,144).


To determine the exponential function


`y=ab^x`


plug-in the given x and y values.


For the first point (2,24), the values of x and y are x=2, y=24. Plugging them, the exponential function becomes:


`24=ab^2`     (Let this be EQ1.)


For the second point (3,144), the values of x and y are x=3 and y=144. Plugging them, the function becomes:


`144=ab^3`     (Let this be EQ2.)


To solve for the values of a and b, apply substitution method of system of equations. To do so, isolate the a in EQ1.


`24=ab^2`


`24/b^2=a`


Plug-in this to EQ2.


`144=ab^3`


`144 = 24/b^2 * b^3`


And, solve for b.


`144=24b`


`144/24=b`


`6=b`


Now that the value of b is known, plug-in this to EQ1.


`24=ab^2`


`24=a*6^2`


And, solve for a.


`24=36a`


`24/36=a`


`2/3=a`


Then, plug-in the values of a and b to


`y=ab^x`


So this becomes


`y=2/3*6^x`


Therefore, the exponential function that passes the given two points is `y=2/3*6^x` .

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