SOLUTION: Find p so that p+7, 3p+9, p+3,... form an arithmetic sequence

Question 1084203: Find p so that p+7, 3p+9, p+3,... form an arithmetic sequence
Answer by ikleyn(52790) (Show Source): You can put this solution on YOUR website!
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Find p so that p+7, 3p+9, p+3 form an arithmetic sequence

Notice that I took off ". . . " from the condition, since it MUST be so, according to the common sense.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This condition is

 = ,   or

(p+3) - (3p+9) = (3p+9) - (p+7),   which implies

-2p - 6 = 2p +2,

-8 = 4p,

p = -2.

Solved.

On arithmetic progressions, see the lessons
    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions
    - Mathematical induction and arithmetic progressions
    - One characteristic property of arithmetic progressions
    - Solved problems on arithmetic progressions
in this site.

Also, you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Arithmetic progressions".

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