Big Ideas Math Algebra 2, 2014
BI
Big Ideas Math Algebra 2, 2014 View details
Chapter Review
Continue to next subchapter

Exercise 28 Page 402

If a horizontal line can intersect the curve at more than one point, then the inverse is not a function. To find the inverse, start by replacing f(x) with y.

Is the inverse a function? Yes
Inverse of the function: g(x)= 3x-6

Practice makes perfect

For the given function, we will first draw its graph and then use the Horizontal Line Test to determine whether the inverse is a function. Then, we will find the inverse. Let's start!

Is the Inverse a Function?

To graph the given function, we should first determine its asymptotes. f(x)=3/x+6 Recall that division by zero is not defined. Therefore, the rational function is undefined where x+6=0. x+6=0 ⇔ x = -6

The above means that x= -6 is the vertical asymptote of the function. To find the horizontal asymptote, let's pay close attention to the degrees of the numerator and denominator. f(x)=3/x^1+6 We see that the degree of the denominator is greater than the degree of the numerator. Therefore, the line y=0 is a horizontal asymptote. Now, we will draw the asymptotes.

Next, we will make a table of values. We will include x-values to the left and to the right of the vertical asymptote.

x 3/x+6 f(x)=3/x+6
- 10 3/- 10+6 - 3/4
- 9 3/- 9+6 - 1
- 8 3/- 8+6 - 3/2
- 7 3/- 7+6 -3
-5 3/-5+6 3
-4 3/-4+6 3/2
-3 3/-3+6 1
-2 3/-2+6 3/4

Let's plot and connect the points.

Finally, we can perform the Horizontal Line Test. If the horizontal lines intersect the graph once, then the inverse is also a function. Conversely, if there is even one horizontal line that intersects the graph more than once, then the inverse is not a function.

We can see above that all the horizontal lines intersect the curve at only one point. Therefore, the inverse of the given function is also a function.

Finding the Inverse

Before we can find the inverse of the given function, we need to replace f(x) with y. f(x)=3/x+6 ⇔ y=3/x+6 Now, to algebraically determine the inverse of the given equation, we exchange x and y and solve for y. Given Equation & Inverse Equation y=3/x+6 & x=3/y+6 The result of isolating y in the new equation will be the inverse of the given function.
x=3/y+6
â–Ľ
Solve for y
x(y+6)=3(y+6)/y+6
x(y+6)=3* y+6/y+6
x(y+6)=3
y+6=3/x
y=3/x-6
Therefore, the inverse of the given function is g(x)= 3x-6.