Challenging all you math experts out there! 10 points to the first to answer correctly!

I just want to do a quick test to see how sharp you are. The fastest person to post the correct answer and describe my formula will get 10 points. Easy as that. Ready?.... GO!!

Tell me the next FOUR numbers in this sequence and describe the formula.

HINT: There are two possible formulas

7, -2, 12, -6, 15, -12, 16, -20, 15, -30, __, __, __, __

12
-42
7
-56

a_0 = 7
a_2 = 12 = 7 + 5
a_4 = 15 = 12 + 3
a_6 = 16 = 15 + 1
a_8 = 15 = 16 - 1
a_10 = 15 - 3 = 12
a_12 = 12 - 5 = 7

a_1 = -2
a_3 = -6 = -2 - 4
a_5 = -12 = -6 - 6
a_7 = -20 = -12 - 8
a_9 = -30 = -20 - 10
a_11 = -30 - 12 = -42
a_13 = -42 - 14 = -56

7, -2, 12, -6, 15, -12, 16, -20, 15, -30, 12,-42, 7, -56 the diference of the numbers are
-9, 14 -18, 21,-27. 28, -36 . 35.-45, 42, -54, 49,-63 if you see the negative numbers are
-9, -18, -27, -36, -45, -54 -63 decreasing 9 in the next and the positive are
14, 21, 28, 35, 42, 49 increasing 7 , so then we find the next four
numbers

The first, third, fifth, seventh... et cetera numbers follow this pattern: +5, +3, +1, -1, -3...
The second, fourth, sixth... et cetera numbers follow this pattern: -4, -6, -8, -10... et cetera

So, it goes:
7, -2, 12, -6, 15, -12, 16, -20, 15, -30, 12, -42, 7, -56.

12, -42, 7, -56

look at the negative numbers and the postive numbers seperately, theres a simple sequence there :)

12, -42, 7, -56

Don't bother "challenging" us. That's less incentive than the points, which don't matter either.

7, -2, 12, -6, 15, -12, 16, -20, 15, -30, 12, -42, 7, -56

Hi there!

12, -42, 7, -56

Hope this helps!

wow ithought iwas good at math...

Do ur own homework

40 cause I used my insticnt...that/s the formulat