Help!!!!!

DTfan · 09-12-2007, 12:03 AM

I have a TI-84 Plus Silver Edition and I need to graph x & y coordinates to do linear programming and I can't figure out how to enter the coordinated to get my graph up. Does anyone have any idea how to do this? I have to get all of my math homework done asap and I can't finish it without doing this.....

GRIZZ · 09-12-2007, 01:39 AM

All I have is a TI-83 and I haven't used it the first time since I've been in engineering school because they say engineers design calculators and we need to do this stuff out in the field if we do not have access to a calculator. If they are similar, you can just punch the Y= sign and type in your equation then push the graph button on the top right below the screen. If not you may wan to hit google up. I use their search engine to find different sites to plot stress-strain and dynamic graphs.

GRIZZ · 09-12-2007, 01:57 AM

I forgot to add, that if the equation works, you can hit the trace button and it will show you what your numbers are at various points along the graph to help you get your answers.

DTfan · 09-12-2007, 08:54 AM

alright my equation is like 60x+25y (less than or equal to) 24,000 plus 20x+5y (less than or equal to)6,000. How do i enter Y. I know how to do x but I have no idea how to do y. I'll ask my instructor this morning nad see what he can tell me. I have to get all of my math homework done tonight and I can't do the rest because I dont know how to graph on my calculator to get the points I need to finish.

GRIZZ · (This post was last modified: 09-12-2007, 10:31 AM by GRIZZ.)

If you have solved for x, plug in that number to the equation. Then take your smaller y and take it to the other side. So from the looks of the equation you should get something like 20y<=24,000 +(20-40)(your x value). Once you get that, divide by 20 and you should get your y. y<=[(24,000-40(x-value))]/20 Not exactly sure how you would solve for two varibles on an x-only graphing calculator. But see if that helps some.

TheyKnowMe · 09-12-2007, 10:28 PM

Do it out manually =)

DTfan · 09-12-2007, 11:56 PM

well i would have originally but my x & y coordinated were in like the upper hundreds so that would've been a really big graph but as it seems my instructor went over a similar problem today in class and i took really good notes and then came back and plugged m numbers in and got it right finally.

GRIZZ · (This post was last modified: 09-13-2007, 12:19 AM by GRIZZ.)

Thats good DT. Any time you have a problem with 2-3 variables such as (X, Y Z or I, J, K), just subtract them out if they are parallel. If not, you can always manipulate an equation by multiplying it by a constant to get a varible to drop out, solve for another variable then plug it back into the equation to get an answer. Then keep that one answer in the equation for the variable, and solve for another. I'm in Calc 3 right now so its been a while since I've had College Algebra and Trig, but anytime you need help feel free to give me a shout.

DTfan · 09-13-2007, 11:24 AM

Yeah, I'll keep that in mind. I got stuck on this one problem last night and it was the only one I had left out of all of my homework and it took me forever. First I had no clue what I was doing but on the website where I have to do my homework there was a link to watch a video which showed an instructor walking you through the steps and it took me a whiel to get the hang of it but after I did it went a little better. I had to graph a parabola that opened up and on the graph it had a tool for side to side parabolas and up and down parabolas and after a while of not getting it right I realized I was using the side to side tool instead of the other one so then it took me 30 minutes to figure out what my vertex was and I just happened to look down at my phone and right there on the paper was where I figured out what the vertex would be... the exact points. So after I plotted the correct vertex and used the right parabola tool the problem went fast. I felt like an idiot though because I had worked on that problem for at least 2-3 hours. But now all of my math homework is done and I have to start studying for my test now.

GRIZZ · 09-13-2007, 01:36 PM

Most of your parabola's that open up are going to be integers raised to the even x-power. They should be symmetrical, but like you said the most difficult part would be finding the exact point of the vertex. I know how you feel about spending so much time on one problem, but when I get stuck I normally step away from it for a bit to take a short break then go back at it when I'm a little fresher. It cuts down on a lot of stress.