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Integration question core 4 June 2011

Is the mark scheme wrong here?

When integrating (1-x)^-2, shouldn't that be -(1-x)^-1?

In the mark scheme it looks like they've missed out the minus sign, or am I doing something wrong?
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Original post by lucyjane_x
Is the mark scheme wrong here?

When integrating (1-x)^-2, shouldn't that be -(1-x)^-1?

In the mark scheme it looks like they've missed out the minus sign, or am I doing something wrong?


Differentiate -(1-x)^-1 and see what you're missing.
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lucyjane_x
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Original post by SeanFM
Differentiate -(1-x)^-1 and see what you're missing.


But in the question it doesn't ask you to differentiate -(1-x)^-1?
Original post by lucyjane_x
But in the question it doesn't ask you to differentiate -(1-x)^-1?


I don't disagree with that statement :lol:

But you tried to work out the integral of (1-x)^-12 by recognising it as something similar to the derivative of (1-x)^-1 (well, exactly that actually but that's not the point).

If you try differentiating your answer to get back to what you're integrating, you will see where the -1 goes.
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lucyjane_x
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Original post by SeanFM
I don't disagree with that statement :lol:

But you tried to work out the integral of (1-x)^-12 by recognising it as something similar to the derivative of (1-x)^-1 (well, exactly that actually but that's not the point).

If you try differentiating your answer to get back to what you're integrating, you will see where the -1 goes.


Omgggg I get it now I forgot to divide by -1 again because it's 1-x lol
Original post by lucyjane_x
Omgggg I get it now I forgot to divide by -1 again because it's 1-x lol


Indeed.. when you differentiate (1-x)^-1 or anything like that, you take the power down like you're differentating x^n and multiply by the derivative of the thing inside the brackets, which is why you get -1 * -1 * .... and.. yeah. That is what I was trying to show you via differentiation for your integration question.
Reply 6
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lucyjane_x
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Original post by SeanFM
Indeed.. when you differentiate (1-x)^-1 or anything like that, you take the power down like you're differentating x^n and multiply by the derivative of the thing inside the brackets, which is why you get -1 * -1 * .... and.. yeah. That is what I was trying to show you via differentiation for your integration question.


yeah thanks lol it's just silly mistakes

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