Thread: how to make Y the subject? Ti-89

Hi to all great members and staff

I was wondering how could I make the Y subject for making a equation for this question with ti 89
this is the straight line equation fill out by numbers:
y-3=-1(x-2/6)
how can I make the subject Y?By using cal, Thanks

Originally Posted by User Name

Hi to all great members and staff

I was wondering how could I make the Y subject for making a equation for this question with ti 89
this is the straight line equation fill out by numbers:
y-3=-1(x-2/6)
how can I make the subject Y?By using cal, Thanks

You're kidding, right? I really do hope you know that to make y the subject you just add 3 to both sides.

Perhaps you meant to ask how to make x the subject (maybe you're trying to find the inverse function). In which case:

solve(y - 3 = -1(x - 2/6), x)

does the trick. However, you really should be able to do this with out using a CAS.

Originally Posted by mr fantastic

You're kidding, right? I really do hope you know that to make y the subject you just add 3 to both sides.

Perhaps you meant to ask how to make x the subject (maybe you're trying to find the inverse function). In which case:

solve(y - 3 = -1(x - 2/6), x)

does the trick. However, you really should be able to do this with out using a CAS.

no mate,
you got me wrong I know the trick you gave me already!
I want the Y as the subject!
like Y= blah blah :d
the one you did gives the value of X!
Thanks

Originally Posted by User Name

no mate,
you got me wrong I know the trick you gave me already!
I want the Y!
like Y= blah blah :d
Thanks

If you really need to use a CAS for that question, then you're going to have big big problems down the track with your maths (assuming you continue with maths down the track). You're strongly advised to work on your 'by-hand' skills now while you still have time.

Originally Posted by mr fantastic

If you really need to use a CAS for that question, then you're going to have big big problems down the track with your maths (assuming you continue with maths down the track). You're strongly advised to work on your 'by-hand' skills now while you still have time.

I can do it "by hand" but i was just trying to save the time!

Also in addition the equation I just gave you it's from straight line equation and the Q wants the normal and the tangent of the equation!
So...
I know that's really easy version! er can solve it by take the 3 to other side, however that's not all it's asking mate,
I will try to scan the original question by tomorrow!
hope you get me:S

Originally Posted by User Name

no mate,
you got me wrong I know the trick you gave me already!
I want the Y as the subject!
like Y= blah blah :d
the one you did gives the value of X!
Thanks

So just write the same thing as mr f, but solving for y... If you knew the trick, you should have understood that !

solve(y - 3 = -1(x - 2/6), y) gives y with respect to x.............

now, for having used my TI-89 for 7 or 8 years, I strongly advise you not to try to save time, for this kind of things.
You will spend less time by doing it by hand than typing it on the calculator.


If you want to check, okay, but don't do that in an exam.

Originally Posted by User Name

Hi to all great members and staff

I was wondering how could I make the Y subject for making a equation for this question with ti 89
this is the straight line equation fill out by numbers:
y-3=-1(x-2/6)
how can I make the subject Y?By using cal, Thanks

Short and sweet lol:

y = -1(x-2/6) + 3

(But if you do know how to do it by hand, home come you didn't just do it??)

Originally Posted by User Name

I can do it "by hand" but i was just trying to save the time!

Huh? It takes a split second to mentally solve for and then you write it down. Your idea is to instead spend several long seconds typing the equation into the calculator, and then to write down the output displayed on the screen? That does not sound very efficient to me.

Guys!

The equation I gave out is made by me with easy setups, the real one in my book is longer and has combined with many other equations!
I KNOW AND I CAN GET THE THE EASY EQUATION SO PLEASE DO NOT SAY THAT'S EASY OR BLAH BLAH, THAT'S MEANT TO BE EASY COZ I MADE IT EASY!!!
i just wanted to use the trick in further and harder equations!
HOWEVER!
I found the trick! by just messing around with my cal like a hour! seems you all didn't know it as well a I! so I share it hear so you'll know it!=)
Here is it:
If you want to make a Y or anything the subject of the equation you just type the equation and enter than press ANS - Y!
Simple!
that's take the Y out so it makes it the equation!Happy)not the gives the VALUE!,Y!

Thanks every one!