A few days ago
Anonymous

Homework/math question… really hard (for me)?

I have to write a formula for the following pattern:

1,5,12,22,35 etc.

(the difference between the numbers goes up by three.. eg. 5-1=4, 12-5=7, 22-12=10 etc.)

I can use as many variables as needed, and I have to find a formula that applies for any given whole number…

Top 1 Answers
A few days ago
John V

Favorite Answer

a_n = a_(n-1) + 3(n-1) + 1 is the general pattern, with a_1 = 1.

So we are adding n-1 multiples of 3, which is 3n(n-1)/2, as well as n 1’s (each a_n) has a 1 in its formula. Thus the formula is n + 3n(n-1)/2.

Try it for 4: 4 + 3*12/2 = 22

5: 5 + 3*20/2 = 35

6: 6 + 3*30/2 = 51

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