Discover new information and insights with the help of IDNLearn.com. Get timely and accurate answers to your questions from our dedicated community of experts who are here to help you.

For the following exercise, use your graphing calculator to find the [tex]$x$[/tex]-intercepts of the graph of this equation:

[tex]\[ y = -2x^2 - 9x + 9 \][/tex]

Method 1: You can use the CALC-Zero feature of your graphing calculator.

Method 2: You can enter the following equations and then use the CALC-Intersect feature of your graphing calculator.
[tex]\[
\begin{array}{l}
Y_1 = -2x^2 - 9x + 9 \\
Y_2 = 0
\end{array}
\][/tex]

Round your answers to three decimal places. Give the larger answer first.

The [tex]$x$[/tex]-intercepts are at:
[tex]\[
(\square, 0)
\][/tex]
[tex]\[
(\square, 0)
\][/tex]


Sagot :

First, given the quadratic equation [tex]\( y = -2x^2 - 9x + 9 \)[/tex], we need to find the [tex]\( x \)[/tex]-intercepts, where the graph of the equation crosses the x-axis. The [tex]\( x \)[/tex]-intercepts occur where [tex]\( y = 0 \)[/tex].

So, we set the equation to zero:
[tex]\[ -2x^2 - 9x + 9 = 0 \][/tex]

We can solve this quadratic equation either using the quadratic formula [tex]\( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \)[/tex] or graphing calculator methods.

### Method 1: Using the CALC-Zero Feature of a Graphing Calculator

1. Enter the Equation:
- Enter [tex]\( y = -2x^2 - 9x + 9 \)[/tex] into the graphing calculator.

2. Graph the Equation:
- Graph the equation to visualize where it crosses the x-axis.

3. Find the Zeros:
- Use the `CALC` menu to select the `Zero` feature.
- For the first intercept, move the cursor near where the graph crosses the x-axis (right intercept) and follow the prompts to find the zero.
- For the second intercept, move the cursor near the other crossing (left intercept) and find the zero.

### Method 2: Using the CALC-Intersect Feature of a Graphing Calculator

1. Enter the Equations:
- Enter [tex]\( Y_1 = -2x^2 - 9x + 9 \)[/tex] into your graphing calculator.
- Enter [tex]\( Y_2 = 0 \)[/tex] (which is simply the x-axis).

2. Graph the Equations:
- Graph both [tex]\( Y_1 \)[/tex] and [tex]\( Y_2 \)[/tex] on the same set of axes.

3. Find the Intersection Points:
- Use the `CALC` menu to select the `Intersect` feature.
- For the first intercept (right intercept), move the cursor near the intersection point on the right and follow the prompts to determine the x-coordinate of the intersection.
- For the second intercept (left intercept), move the cursor near the intersection point on the left and find the x-coordinate.

After using one of the methods, we find the x-intercepts are approximately:
- [tex]\( x = 0.842 \)[/tex]
- [tex]\( x = -5.342 \)[/tex]

### Solution:
The [tex]\( x \)[/tex]-intercepts, ordered with the larger value first, are:

[tex]\[ (0.842, 0) \][/tex]
[tex]\[ (-5.342, 0) \][/tex]