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C1 Maths Help: Surds - Where did I go wrong in this question?

10/r5 + 4/r5-r7

10r5-10r7 + 4r5/r5(r5-r7)

14r5 – 10r7/5 – r35

(14r5 – 10r7)(5 + r5r7)

70r5 + 70r7 – 50r7– 70r5

20r7



Should be -2r7
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I can't follow this. If you write it up in LaTeX or upload an image I may be able to help you.
Do them seperatley then put them together. So do 10r3/r15 first to get 2r5. then do the second bit to get -2r5 -2r7.
put then together to get

2r5 - 2r5 - 2r7

the 2r5 and -2r5 cancel so you are left with -2r7

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Hope that helps :smile:

Posted from TSR Mobile
Original post by ImNervous
Do them seperatley then put them together. So do 10r3/r15 first to get 2r5. then do the second bit to get -2r5 -2r7.
put then together to get

2r5 - 2r5 - 2r7

the 2r5 and -2r5 cancel so you are left with -2r7

Posted from TSR Mobile


Ah thank you sooo much! You're fantastic! :biggrin::biggrin:
No problem

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Original post by creativebuzz
10/r5 + 4/r5-r7

10r5-10r7 + 4r5/r5(r5-r7)

14r5 – 10r7/5 – r35

(14r5 – 10r7)(5 + r5r7)

70r5 + 70r7 – 50r7– 70r5

20r7



Should be -2r7


Multiply both sides by the second denominator over the second denominator but with a plus sign (it's pair)
(edited 9 years ago)

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