ncjjancdaklcnlc

stamina9008

cbjkancljancjkancljk

somethingcorporate

y = (x -3) /4

multiply both sides by 4

4y = x - 3

add 3 to both sides

4y + 3 = x

y= 3t(t+x)

divide through by 3t

y/3t = t+x

take t from both sides

y/3t - t = x

Linton

stamina9008 wrote: »

Hi, im really struggling with these 'Change The Subject Of A Formula' questions.
Im okay on the most of them, but these two have me stumped, especially the first one because there is nothing outside of the bracket to multiply it by and expand it..and...its on its own above a divide sign...im so stupid [please help..

Make x the subject

y = (x -3) /4


Make x the subject

y= 3t(t+x)

1)

Multiply by 4:

4y=x-3

Add 3 and swap side:

x=4y+3

2)

Divide by 3t:

y/3t=t+x

Subtract t and swap sides

x=y/3t - t


And this is GCSE!!!!!

WestonDave

y= (x-3)/4
4y = (x-3)
4y+3 = x
x=4y+3

y = 3t(t+x)
y/3t = t+x
(y/3t)-t = x
x=(y/3t)-t

Strictly speaking the brackets on the last line of the 2nd one aren't necessary as you'd write it as a fraction -t but for clarity in typing rather than handwriting...

The old way of doing these was "do the same to both sides" so to get rid of the "divide by 4" you multiply both side by 4 which means the right hand side divide and multiply cancel leaving 4x on the left. You then add 3 to both sides which cancels on the right and leaves +3 on the left.

Similarly with the second one which might confuse by expecting the t's to simplify - they won't as they have different operations.

Now lets see how much O-level maths I can remember after 20+ years when others pick this apart.

stamina9008

Thanks guys, you've really helped and also, you explained it very simply and in stages..
Ive copy and pasted what you wrote, thanks!

somethingcorporate

3 answers all the same bodes well!

Linton

stamina9008 wrote: »

Thanks guys, you've really helped and also, you explained it very simply and in stages..
Ive copy and pasted what you wrote, thanks!

Perhaps you should write it down on your own so that you are sure you understand how to do these sorts of problems rather than just copy and paste.

stamina9008

Hi,
Well, i copied and pasted it to notepad and now im rewriting it on blank paper and following the steps.
I know it may be easy for some, but, some of us arent as quick as others.
Have a nice day.

getmore4less

The way I do/think is


anything in the form A/B becomes B/A

move above to below(below to above)

OR anything in the form +A-B becomes -A+B

change the sign when moving left to right

Anyway to address your key problem which was this

especially the first one because there is nothing outside of the bracket to multiply it by

y = (x -3) /4
becomes
y= x/4 - 3/4
Y+3/4 = x/4
4(Y+3/4) = x
4Y + 3


Allthough not needed in this case there are other more complicated equations where this technique can be usefull.

agrinnall

Does anyone else think it's morally wrong to be doing somebody's homework for them? How is the OP going to learn how to do it if every time something new comes along they take the easy option of getting the answer online? No wonder employers complain about the standard of school leavers.

Sambucus_Nigra

agrinnall wrote: »

Does anyone else think it's morally wrong to be doing somebody's homework for them? How is the OP going to learn how to do it if every time something new comes along they take the easy option of getting the answer online? No wonder employers complain about the standard of school leavers.

Totally agree.

What's the point otherwise?