Math Is Fun Forum / Algebra -Subject

Al-Allo · 2013-03-08 08:14:55

Hi

s = ut +½at^2

So I want you to tell me why my way of doing is wrong : (a must be the subject)

-ut s = ut +½at^2 -ut

/ ½t^2 s-ut=½a^t2 / ½t^2 (This is how I think I should have done it, because we want only the a, so you divide all in one shot)

s-ut/ ½t^2=a ===> a=s-ut/ ½t^2

I Know this is the wrong answer, but explain me why my way of doing is wrong, because I have no idea why ! Thanks

bobbym · 2013-03-08 08:27:04

Hi;

Is this the question?

You want to solve for a?

Al-Allo · 2013-03-08 08:29:58

I want 'a' to be the subject of the formula, I already did my way of doing, which is wrong, and would like to know wy it's wrong. Thanks

bobbym · 2013-03-08 08:33:16

Hi;

Just trying to get the exact question. You want a on the left by itself and that is the correct form in post #2.

This is the answer.

Last edited by bobbym (2013-03-08 08:36:09)

Al-Allo · 2013-03-08 08:37:05

Yes, that's what I want, 'a' on the left of the formula.

bobbym · 2013-03-08 08:43:02

Hi;

Times everything by 2

Subtract 2ut from both sides

Divide by t^2.

Clean up.

Al-Allo · 2013-03-08 08:47:20

Oh wow.....It's clear now ! I understand now ^^ thanks. The way you present the formula is more clean, I got misleaded by my mess lol

bobbym · 2013-03-08 08:50:06

Hi;

Just remember I treated it algebraically. Like a bunch of letters. t must never be zero.

Al-Allo · 2013-03-08 09:08:11

Ok, by curiosity, do you know where I could practice more of these ?

bobbym · 2013-03-08 09:09:14

I could give you a few if you want or I will look up a page if there is one.

Al-Allo · 2013-03-08 09:13:50

That would be great, always looking to practice Anyway, I need to go
! BYe

bobbym · 2013-03-08 09:18:17

Okay, here are three.

Make a the subject.

Or

Make b the subject.

And last!

Make b the subject.

Last edited by bobbym (2013-03-08 09:34:30)

Al-Allo · 2013-03-09 04:23:16

i did the first one

a=s-ut^2

btw, do you have an article on these ? im having a hard time doing these ^^ ty

a(x)a-x/-2=b

b=1/u.a

Last edited by Al-Allo (2013-03-09 04:33:59)

bobbym · 2013-03-09 12:26:21

I made them up for you.

You should get

Last edited by bobbym (2013-03-09 12:26:48)

Al-Allo · 2013-03-09 15:45:36

Oh man, I don't know why but I'm having trouble with these. I dont know where to begin and always get a different answer >.< And what I meant by article is something that tells how to approach rearranging formulas

bobbym · 2013-03-09 19:09:17

Hi;

Follow along with what I do:

Subtract u from both sides.

Clean the denominator on the right, t*a*t^2 = a*t^3.

Multiply both sides by a

Divide both sides by (s - u)

Last edited by bobbym (2013-03-09 19:22:11)

Al-Allo · 2013-03-10 04:30:31

is the third one a=ub/2 ??? hope i got it

anonimnystefy · 2013-03-10 04:32:23

Hi Al-Allo

You should have a on the left hand side. And the expression you got that isn't correct either.

bobbym · 2013-03-10 04:32:45

Hi;

That is not correct. What was your first step?

Al-Allo · 2013-03-10 04:38:11

here is what I did : (like I said, Im not sure how to begin these, to many steps, but the simple ones I can easily do them)

*bu 1/a=1/b+1/u *bu

*a 1/a *bu= 2 *a

bu/2=2a/2

a=bu/2

Last edited by Al-Allo (2013-03-10 04:38:31)

bobbym · 2013-03-10 04:42:21

Hi;

Okay, let's follow your idea and times both sides by bu.

You should get:

Last edited by bobbym (2013-03-10 04:42:39)

Al-Allo · 2013-03-10 04:44:39

OKay, but isn't it supposed to be 1+1 on the right side ?...

bobbym · 2013-03-10 04:49:08

Hi;

No, you are cancelling too much. let's see what happens just on the left.

Now cancel the b in the first fraction.

Are you okay up to here?

Al-Allo · 2013-03-10 04:51:29

AHHHHHHHHHH... okay that why. Mh bobbym, could we continue later this way of doing ? Because I need to go like now. We shall continue later, when I'm online ? Thanks for your help

bobbym · 2013-03-10 04:59:18

Okay, I will see you later. Have a good day.

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#1 2013-03-08 08:14:55

Algebra -Subject

#2 2013-03-08 08:27:04

Re: Algebra -Subject

#3 2013-03-08 08:29:58

Re: Algebra -Subject

#4 2013-03-08 08:33:16

Re: Algebra -Subject

#5 2013-03-08 08:37:05

Re: Algebra -Subject

#6 2013-03-08 08:43:02

Re: Algebra -Subject

#7 2013-03-08 08:47:20

Re: Algebra -Subject

#8 2013-03-08 08:50:06

Re: Algebra -Subject

#9 2013-03-08 09:08:11

Re: Algebra -Subject

#10 2013-03-08 09:09:14

Re: Algebra -Subject

#11 2013-03-08 09:13:50

Re: Algebra -Subject

#12 2013-03-08 09:18:17

Re: Algebra -Subject

#13 2013-03-09 04:23:16

Re: Algebra -Subject

#14 2013-03-09 12:26:21

Re: Algebra -Subject

#15 2013-03-09 15:45:36

Re: Algebra -Subject

#16 2013-03-09 19:09:17

Re: Algebra -Subject

#17 2013-03-10 04:30:31

Re: Algebra -Subject

#18 2013-03-10 04:32:23

Re: Algebra -Subject

#19 2013-03-10 04:32:45

Re: Algebra -Subject

#20 2013-03-10 04:38:11

Re: Algebra -Subject

#21 2013-03-10 04:42:21

Re: Algebra -Subject

#22 2013-03-10 04:44:39

Re: Algebra -Subject

#23 2013-03-10 04:49:08

Re: Algebra -Subject

#24 2013-03-10 04:51:29

Re: Algebra -Subject

#25 2013-03-10 04:59:18

Re: Algebra -Subject

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