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lilsis76

  • 3 years ago

the sum of three consecutive terms in an arithmetic sequence is 30, and their product is 360. Find the three terms. Let x denote the middle term and d the common difference. well i got so far: ______+________+__________= 30 but ______x________x__________=360 ya, thats as far as I got and i am still stumped. I tried all kinds of things but i cant seem to get the right sum and multiplied values

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  1. cnknd
    • 3 years ago
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    middle term must be 10

  2. lilsis76
    • 3 years ago
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    do i divide by 36? how do i know what to put in for the middle parts? i remember class mates saying something by going up or down by a k, or a 1 or something. is there a rule or something like that I have to know?

  3. cnknd
    • 3 years ago
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    ok, using your notation, x is the middle term, d is the common difference: (x-d) + x + (x+d) = 30. so what's x?

  4. lilsis76
    • 3 years ago
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    okay so the the left would be negative and the right would be positive.

  5. lilsis76
    • 3 years ago
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    okay @cnknd would it be 10-5 + 10 + 10+5 = 30?

  6. cnknd
    • 3 years ago
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    ugh... what???? ok take a step back, forget i told u that middle term is 10. look at the equation for the sum: (x-d) + x + (x+d) = 30 can u find x and d from this?

  7. lilsis76
    • 3 years ago
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    okay well i was thinking the 30/3 = the 10

  8. lilsis76
    • 3 years ago
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    @cnknd okay the d is the difference and x is the actual number. i am lost as to where to start

  9. cnknd
    • 3 years ago
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    (x-d) + x + (x+d) = 30 can you solve for either x or d?

  10. lilsis76
    • 3 years ago
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    i think we can solve the x. the 3x= 30 so x=10, right?

  11. cnknd
    • 3 years ago
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    yes but you can't really determine what d is though.

  12. cnknd
    • 3 years ago
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    but at least now you know why the x (the middle number) is 10.

  13. cnknd
    • 3 years ago
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    you can probably guess and check for the other 2 numbers (that's what i did)

  14. lilsis76
    • 3 years ago
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    okay, let me try and ill get back to you on this in a little

  15. lilsis76
    • 3 years ago
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    GOT IT! (10-8) +/* 10 +/* (10+8) +=30 * =360

  16. lilsis76
    • 3 years ago
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    THANK YOU SO MUCH @cnknd

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