Big Ideas Math Integrated I, 2016
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Big Ideas Math Integrated I, 2016 View details
1. Exponential Functions
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Exercise 63 Page 280

Use the Slope Formula.

Example Function: f(x)=5^x

Practice makes perfect
We want to write an exponential function so that the slope from the point (0, f(0)) to the point (2, f(2)) is equal to 12. Let's move the points so that the slope between the points is 12 and that the x-coordinates of the points are 0 and 12.
Now, we have an idea about how the graph changes as the points change. Using the Slope Formula, we can write the following equation. m=y_2-y_1/x_2-x_1 ⇒ 12=f(2)-f(0)/2-0Let's simplify it.
12=f(2)-f(0)/2-0
12=f(2)-f(0)/2
24=f(2)-f(0)
Since f(x) is an exponential function, it has the form f(x)=a(b)^x. Then, f(2)=a(b)^2 and f(0)=a(b)^0. f(x)=a(b)^x ⇒ lf(0)= a(b)^0 f(2)= a(b)^2 Let's substitute the equivalent expressions.
24=f(2)-f(0)
24= a(b)^2- a(b)^0
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Factor RHS
24=a(b)^2-a(1)
24=a(b)^2-a
24=a(b^2-1)
24=a(b+1)(b-1)
If we let a be equal to, for example, 1, then we have the following equation. 24 =a(b+1)(b-1) ⇓ 24 =(b+1)(b-1) We need to find two factors whose difference is 2 and product is 24. For example, 6 and 4. 24 = (b+1)_6 (b-1)_4 ⇒ b=5 Therefore, b is 5. We can now substitute a=1 and b=5 into the function form. f(x) = a (b)^2 ⇒ f(x) = 1(5)^x This exponential function satisfies the desired condition. Please note that we can find different functions for this exercise.

Checking Our Answer

Checking Our Answer

Let's first find the points on the exponential function when x=0 and x=2.

f(x)= 5^x
Operation x=0 x=2
Substitution f( 0)= 5^0 f( 2)= 5^2
Point (0,1) (2,25)
Now, we can calculate the slope from (0,1) to (2,25).
m = y_2-y_1/x_2-x_1
m = 25- 1/2- 0
m = 24/2
m = 12
The slope is equal to 12, so we found a correct function.