Really fast (and easy) maths help! PLEASE!?

Okay, I have a test tomorrow which is worth only like 5% of my overall maths grade, but I really don't want to fail (it's 2 credits, and I need 80 at the end of the year).

Just fast:

In my textbook (for an example) it says: a: 23, d: 6, n: ?

Tn= a + (n-1) d

Tn= 23 + (n-1) 6

Tn= 6n + 17

I don't understand how it jumps from 23 + (n-1)d to 6n + 17.

PLEASE PLEASE EXPLAIN! Oh no :(

2 Answers

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  • 9 years ago
    Favorite Answer

    here a(23) is the first term of AP

    d(6) is the common difference

    Tn is the nth term of the AP

    the AP thus =23,29,35,41,47.....

    here 5th term is 47, ie n=5. To find the 5th term , write the formula

    Tn=a+(n-1)d and put the values of a,d and n.

    T5=23+(5-1)*6

    T5=23+4*6

    T5=23+24

    T5=47

    that is ie 5th term of AP=47

    similarly if you want to find the 100th term of AP ie n=100, then

    T100=23+(100-1)6

    T100=23+99*6

    T100=23+594

    T100=617. Hope it helps .Good luck .

  • 9 years ago

    what they did is opened the bracket

    ie. 23+6n -6

    ie. 6n+17

    all the best 4 ur exam

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