math

The fourth term of an ap is 1 less than twice the second term. If the sixth term is 7, find the first term.

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  1. Just translate into Math using your definitions of an AP
    a+5d = 7 **

    a+ 3d = 2(a+d) - 1
    a + 3d = 2a + 2d - 1
    -a + d = -1 ***

    add ** and ***
    6d = 6
    d = 1
    back in **
    a + 5=7
    a = 2

    the first term is 2

    check:
    sequence is 2,3,4,5,6,7,8, ...
    Is the fourth term less than twice the second by 1 ? YES
    Is the 6th term equal to 7 ? YES
    All is good.

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  2. The forth term of an A.P is one less than twice the 2nd term. If the sixth term is 7, find the first term

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