Question

@jhonyy9

Answer 1

Look at the given quadratic equation, y=f(x)=2x^2 - 6x - 9

How would you determine the y-intercept? Hint: what is the x-value at any y-intercept?

Answer 2

2

Answer 3

2 is the coefficient of the x^2 term.
The standard way to find a y-intercept is to let x=0.

Do that, please. f(0)=?

Answer 4

Write the coordinates of the y-intercept, please, as ( x , y ) .

Answer 5

0,6

Answer 6

@mathmale

Answer 7

that'd be perfect if you'd please enclose those coordinates inside parentheses.

y-intercept: (0, 6).

What next? Let's find the x-intercepts. Note well that y=0 at any x-intercept.

Answer 8

Therefore, take the given quadratic function and set it = to 0:\[2x^2-6x-9=0\]

Answer 9

How would you go about solving this?

Note that the instructions say: "Express your answers to the nearest tenth."

That's a hint that the x-intercepts (roots, solutions) are not nice integers, but rather that they have decimal fractions that have to be rounded off to the nearest tenth.

Can you write out the generalform of the quadratic equation? That's an appropriate tool to apply here.

Answer 10

Fine. You can use your TI-84 to approximate the roots.
Have you graphed quadratic equations before, on y our calc?
If so, please type in 2x^2-6x-9 and graph it.

Answer 11

I get x=0 and y=-9

Answer 12

Your equation is 2x^2-6x-9 = y

If x=0, what is y?

Note that this is not the minimum.


y = ?

Answer 13

6

Answer 14

It's the y intercept

Answer 15

x=0

Answer 16

My apologies!! You were right: The y-intercept is indeed (0,-9).
Earlier, you proposed that something was (0,6). What was that?

Answer 17

Sorry the Mica practice test is formatted in a unusual way.

Answer 18

Your equation is 2x^2-6x-9 = y

If x=0, what is y?

Note that this is not the minimum.


y = ?

You responded with "6."

No. When x=0, y=-9. The y-intercept is (0,-9).

Now, you want to use your calculator to find the x-intercepts?

Have you already graphed f(x)=2x^2-6x-9?

Answer 19

Yes, I have graphed the function.

Answer 20

Good. Now press "2nd" and "CALC"

Answer 21

Alright :)

Answer 22

You are looking for zeros (otherwise known as x-intercepts or roots).

Can you take a quick look at your graph and by eye estimate where the left root is located? For example, you could say, "It's located between -2 and -1."

Answer 23

Where is the right root located? Estimate it, or say, "it's between and ."

Answer 24

it's between -1 and 4

Answer 25

Could you be a bit more precise? On my calculator I see the zero is between 4 and 5.

Answer 26

-1 and 4 is too large an interval for this purpose.

Answer 27

I don't know what you're doing with your time, but it seems there are gaps of several minutes or more (much more) between your responses. I would stick with you until you'd finished this problem if you were to give it your full attention. I'm getting off the 'Net now. If you haven't solved this problem by the time I'm back on, tag me.