Graphs and Relations

[fizza106]

Hi legends.
Just wondering if anyone know what the hell these questions are, keep on coming up in practice exams??
Are they in the study design?
Please help, I am desperate!

[zofromuxo]

These question are simultaneous equations.
They are in study design, they are part of the Linear Equation Modules.

I'm guessing this how you do these questions, I'm not 100% certain on how to do these questions. So tread carefully with the methods outlined below.

There are 2 ways of doing this question.
1) Calculator method.
You can plug all the values into your calculator and solve it.
This could be done by attempting to graph the equation and trying to find if the point intersect.
This will then allow you to figure out the fesabile region and thus give you the answer your looking for.

2) Manual method.
You can manually do simultaneous equations for each of them.

[Bri MT]

If there are different formulas based on what the horizontal axis is, this is known as a hybrid function. I'm not familiar with Casio, but on the ti-inspire there is a button which allows you to enter hybrid functions

[fizza106]

Thanks so far guys  but....
How do I enter them in to the calculator?
As..
25t > 2
Or?? The ti-calculator function you are talking about?

[Bri MT]

Thanks so far guys  but....
How do I enter them in to the calculator?
As..
25t > 2
Or?? The ti-calculator function you are talking about?

One of the calculators used by a lot of year 12 math students has "TI-nspire" written on the top of it.

If you have the ti-nspire, the button below the "del" key and next to the book will show you a bunch of options when you open it, including a fraction an a square-root symbol. You are looking for the option with a curly bracket on the left and 6 squares.
When you press that, it will bring up a screen saying "create piecewise function" (piecewise function is the same thing as a hybrid function)
The number of function pieces is the number of rows you need (for this question, 3)
Then press ok. You type in the formula on the left, and write the domain after the comma


The process above allows you to enter the formula into the CAS
You can do   solve( *enter the hybrid function as per instructions above* [press right until the cursor is at the bracket] , (thing/s you are solving for) )      as you would for any other function
You can also define f1(x) or f2(x) etc as being the hybrid function, which means the graph screen will show that function   (this works for any function not just hybrid)

Hope this helps

[fizza106]

Sorry to be annoying, but it says its a syntax when I enter the exact equation! 

[Bri MT]

Sorry to be annoying, but it says its a syntax when I enter the exact equation! 

Is there any information from earlier in the question which might be relevant?
the problem your calculator is having is that you're essentially asking it to solve y=4x+c  , it just doesn't have enough info to know what to do

[zofromuxo]

Ahh, this is where my helps ends fizza.
I sadly own a Classpad and have no idea how to work a Ti-nspire .
I wish I could have been of more help to you, sorry.

[Shadowxo]

Where's this question from? I believe it's worded quite badly, because P is in dollars for the day's work. So if she worked 1 hour, P=25 so she'd earn $25 but if she worked 2 hours P=0 so she'd earn nothing for the day, which I don't believe is what they want to achieve. Probably a mistake in the question
I'll assume that P=50 - that is, she doesn't get paid between 2 and 2.5 hours. (The end of the first function is at t=2 which corresponds to P=50)

This function is (presumably) continuous so the start of the third function would have to be the same as the end of the second function, so P=50 when x is just larger than 2.5 (just larger so that the value is essentially 2.5 but in the domain of the third function)
30*(2.5)+c=50
c=-25

The reason your calculator won't give you an answer is because it doesn't really make sense what you're asking it to do. You're giving it a few (unrelated) equations and asking it to find c. For a question like this it'd be easier to work out by hand or just ask it to solve the equation like 30*2.5+c=50 (assuming I've interpreted the question correctly).