need help with finding the rth term

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parisnaomi
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the question is: find the rth term and the sum to n terms of these series

(3 X -2) + (5 X -1) + (7 X 0) + ...

my answer for the rth term is (2r+1)(r-3). i dont see how this is wrong, but the answer says (2r-1)(n+3). [and the n isnt a typo on my part. both n and r are part of the answer which i dont understand either]

and then, for the sigma notation they use (2r-1)(2r+1)??

is this just a typo or am i missing something...
Last edited by parisnaomi; 8 months ago
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mqb2766
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(Original post by parisnaomi)
the question is: find the rth term and the sum to n terms of these series

(3 X -2) + (5 X -1) + (7 X 0) + ...

my answer for the rth term is (2r+1)(r-3). i dont see how this is wrong, but the answer says (2r-1)(n+3). [and the n isnt a typo on my part. both n and r are part of the answer which i dont understand either]

and then, for the sigma notation they use (2r-1)(2r+1)??

is this just a typo or am i missing something...
Can you upload an image of the question / solution?
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parisnaomi
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(Original post by mqb2766)
Can you upload an image of the question / solution?
Name:  7AB1FE25-B222-44C3-8D0B-E6BB259CD5CD.jpeg
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Size:  98.7 KBName:  52A24FC1-50CC-4C1B-A0B4-1B2E24A15E73.jpeg
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question 6b
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mqb2766
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Yup, the answer is wrong for the rth term and you're correct.
Last edited by mqb2766; 8 months ago
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parisnaomi
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(Original post by mqb2766)
Yup, the answer is wrong for the rth term and you're correct.
okay thank youuu
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