# Thread: Trouble with homework problem

1. ## Trouble with homework problem

I am having difficulty with this problem from my homework. Use a graphing calculator to solve the given equation, 4x2 – 2x – 3 = 0. I am missing something here in my method. Without giving the answer can someone show how they would start this problem? I am rusty at this, its been a long time since I has a math course.

2. Originally Posted by cross1933
I am having difficulty with this problem from my homework. Use a graphing calculator to solve the given equation, 4x2 – 2x – 3 = 0. I am missing something here in my method. Without giving the answer can someone show how they would start this problem? I am rusty at this, its been a long time since I has a math course.
Not knowing what kind of calculator you have, it might be difficult to answer your question.

Using a TI-84+, enter the equation using the Y= key

$Y_1=4x^2-2x-3$

Press the GRAPH key.

Press 2nd and then the TRACE key to bring up the CALC menu.

Choose 2: zero

Using the left arrow key, move the 'spider' to just above the left x-intercept and press ENTER to mark the left bound side of your zero, then move the spider just below the x-intercept and press ENTER to mark the right bound side of your zero. Press ENTER once more to reveal the zero (x-intercept).

You should've gotten -.6513878

That's rounded off, because the exact answer is irrational. Use the quadratic formula to verify this.

You need to repeat this process for the other zero.

By the way, the spider is that blinking asterisk of a thing that is tracing the curve when you use the left or right arrow keys.

3. Originally Posted by masters
not knowing what kind of calculator you have, it might be difficult to answer your question.

Using a ti-84+, enter the equation using the y= key

$y_1=4x^2-2x-3$

press the graph key.

Press 2nd and then the trace key to bring up the calc menu.

Choose 2: Zero

using the left arrow key, move the 'spider' to just above the left x-intercept and press enter to mark the left bound side of your zero, then move the spider just below the x-intercept and press enter to mark the right bound side of your zero. Press enter once more to reveal the zero (x-intercept).

You should've gotten -.6513878

that's rounded off, because the exact answer is irrational. Use the quadratic formula to verify this.

You need to repeat this process for the other zero.

By the way, the spider is that blinking asterisk of a thing that is tracing the curve when you use the left or right arrow keys.
ti-83

4. same keystrokes ... 83 is not much different than an 84

5. Originally Posted by cross1933
ti-83
It should work with TI-83 the same way.

6. Originally Posted by cross1933
ti-83
"You should have come up with -.6513878"

My first calculation came up with X=1.15?

7. Originally Posted by cross1933
"You should have come up with -.6513878"

My first calculation came up with X=1.15?
you found the greater root ... note that there is another root at about x = -.65

8. Originally Posted by skeeter
you found the greater root ... note that there is another root at about x = -.65
I picked up a book today(The Complete Idiot's Guide to Precalculus), maybe this will shed some light on the subject. After the problem is over I look back and wonder what I did to get that answer. I think it has to do with confidence, this can only come with repeated work.

Thanks for the help!

9. The "solutions" are the x-intercepts. So look for where the graph crosses the x-axis.

10. Originally Posted by stapel
The "solutions" are the x-intercepts. So look for where the graph crosses the x-axis.
The answer is right there in front of me. It comes back to lack of confidence from lack of experience. Thanks everyone for your help, I am sure I will be back many times with more questions on different problems.