# Maths rearranging formula Q

Watch
Announcements
#1
make x the subject: ax = b - x
answer: x = b / a + 1
This is my working, where did I go wrong?
ax = b - x
ax + x = b
2x = b / a
x = b / a / 2
x = a / b
0
2 months ago
#2
(Original post by RedVelvet16)
make x the subject: ax = b - x
answer: x = b / a + 1
This is my working, where did I go wrong?
ax = b - x
ax + x = b
2x = b / a
x = b / a / 2
x = a / b

In red's fine, but the line thereafter isn't.

Try taking out the x as separate factor, and hopefully all will be clear.
1
2 months ago
#3
(Original post by RedVelvet16)
ax + x = b
2x = b / a
It’s going from this line to the next, it manipulating algebra doesn’t work like that Can you factorise ax+x ?
1
#4
(Original post by laurawatt)
It’s going from this line to the next, it manipulating algebra doesn’t work like that Can you factorise ax+x ?
is it x(a+1)?
1
#5
(Original post by ghostwalker)
In red's fine, but the line thereafter isn't.

Try taking out the x as separate factor, and hopefully all will be clear.
ax + x = b
a + x = b / x
x + x = b / a ?
0
2 months ago
#6
No. Like you said, x(a + 1) = b

Then that will become...
0
#7
(Original post by sweetescobar)
No. Like you said, x(a + 1) = b

Then that will become...
x(a + 1) = b
x = b / a + 1

ahh that makes more sense now thank you!!
0
2 months ago
#8
(Original post by RedVelvet16)
is it x(a+1)?
Yes, so we have x(a+1) = b
Can you see the last step?
1
2 months ago
#9
(Original post by RedVelvet16)
is it x(a+1)?
yes
1
#10
(Original post by laurawatt)
It’s going from this line to the next, it manipulating algebra doesn’t work like that Can you factorise ax+x ?
yes, it makes sense now; thank you!!
1
#11
Thanks everyone -- I understand now!
Would I always have to factorise?
0
2 months ago
#12
Always, whenever you are trying to rearrange for a variable there is two of, get them on the same side, and factorise
1
#13
(Original post by sweetescobar)
Always, whenever you are trying to rearrange for a variable there is two of, get them on the same side, and factorise
thanks so much! that really helps with the other questions in my textbook!
0
2 months ago
#14
No problem.
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### How would you feel if uni students needed to be double vaccinated to start in Autumn?

I'd feel reassured about my own health (33)
15.21%
I'd feel reassured my learning may be less disrupted by isolations/lockdowns (66)
30.41%
I'd feel less anxious about being around large groups (25)
11.52%
I don't mind if others are vaccinated or not (18)
8.29%
I'm concerned it may disadvantage some students (12)
5.53%
I think it's an unfair expectation (60)
27.65%
Something else (tell us in the thread) (3)
1.38%

View All
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.