I keep getting the error no sign change on my TI 84 plus. i am trying to find the intersect of y=5/28 and y=(0.85)^(X-1). am i doing something wrong?

You enter a command. It is like an English sentence with a syntax (correct structure). If the structure of the command is wrong, you have a syntax error. You could use a minus - sign, instead of a change sign (-) that constitutes a syntax error.

Make sure the argument is between negative one and positive one, inclusive. The inverse cosine is defined only for arguments in that domain, anything else will give you a domain error.

The solve( function was not able to find the intersection point because it lies outside the graph range. The window dimensions are too narrow to contain that point. I suggest you restrict the graph to the quadrant where you suspect the solution to be (example first quadrant if appropriate) : take Xmin=0, Ymin =0 and choose Xmax and Ymax large enough to enclose the intersection point.

If I'm understanding you correctly, you want to graph something like

5x+3=9

If this is correct, graph 5x+3 in the y1 line and 9 in the y2 line. To find the solution, you will press 2nd, then trace the intersection and hit enter 3 times. This will get the solution you need for the equation.

If this is not what you are wanting to do, you need to be try again and elaborate more.

i think there are programs but with something as simple as that you should be able to work it out manually....
3x+25-5x=5x-5x
-2x+25-25=0-25
-2x=-25
x=25/2 or 12.5

The calculator only displays from -10 to 10 on the x and y axes, and both of your lines are outside of that range. However, it is easy to change that.

1. Hit the gray "WINDOW" button that is directly under the screen
2. Change "Xmax" to 150
3. Change "Ymax" to 200

Remember to change both of those values back to 10 when you are done with this problem!

Here's how to graph it:
1. Hit the "Y=" button
2. Enter your first equation after Y1, and your second equation after Y2
3. Look over both the equations to make sure you typed them correctly
4. Hit the "GRAPH" button
5. If you don't see the intersection you will need to adjust Xmax and Ymax again
6. Hit Hit "2ND" and the "TRACE" to bring up the "CALC" menu
7. Scroll down to "intersect" and hit enter
8. Hit enter 3 times (You use the first and second curve options when you have more than 2 lines)
9. It should display the coordinates at the bottom
10. I got (76, 142.1) for the intersection

Thanks for asking this question! I used to do this a much harder way, but while I was calculating the answer to your question I hit a wrong button and accidentally found this method!

-0.171x+43.43 and -0.146x+39.83
i tried that and i got the same thing, but i noticed that if you change your window so it fits more of the graph on the right, were you can actually see the lines intersect, then you can get the intersection.
oh, and by the way, the intersection is (144, 18.806)

make sure your stat plots are off. you can just reset your calc. second + 7 1 2. or you can hit second y= and make sure that the stat plots are off. have any more questions. just send me a another request.

This is my first post on this site, but I've had friends at school ask me about this. Apparently I'm like a calculator genius or something...

One solution I know of is clearing the RAM. Sounds strange, doesn't it? But it fixed three different calcs.

Be sure to back up or archive important data before doing this.