RedVelvet16
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#1
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#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
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ghostwalker
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#2
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#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.
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laurawatt
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#3
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(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 ?
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RedVelvet16
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#4
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(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)?
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RedVelvet16
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#5
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(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 ?
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sweetescobar
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No. Like you said, x(a + 1) = b

Then that will become...
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RedVelvet16
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(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!!
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laurawatt
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(Original post by RedVelvet16)
is it x(a+1)?
Yes, so we have x(a+1) = b
Can you see the last step?
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mnot
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(Original post by RedVelvet16)
is it x(a+1)?
yes
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RedVelvet16
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#10
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(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!!
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RedVelvet16
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#11
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Thanks everyone -- I understand now!
Would I always have to factorise?
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sweetescobar
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Always, whenever you are trying to rearrange for a variable there is two of, get them on the same side, and factorise
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RedVelvet16
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#13
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(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!
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sweetescobar
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No problem.
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