SOLUTION: Find the rule for the mapping if R maps unto A 2 3 4 5 | | | | 1 3 6 10. Nb.R>1 and is a natural number. Thanks

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Question 1143563: Find the rule for the mapping if R maps unto A
2 3 4 5
| | | |
1 3 6 10.

Nb.R>1 and is a natural number. Thanks
Found 2 solutions by greenestamps, ikleyn:
Answer by greenestamps(13200) (Show Source):
You can put this solution on YOUR website!

(2(2-1))/2 = 2/2 = 1
(3(3-1))/2 = 6/2 = 3
(4(4-1))/2 = 12/2 = 6
(5(5-1))/2 = 20/2 = 10

The rule is

(n(n-1))/2

Answer by ikleyn(52804) (Show Source):
You can put this solution on YOUR website!
.

The rule f(n) = pointed by the tutor @greenestamps, is not a unique rule for this map. There are INFINITELY MANY other rules that provide the same map. For example, all the polynomials F(n) = + m*(n-2)*(n-3)*(n-4)*(n-5) with any constant real (or integer) coefficient "m" produce the same map. Notice that the added polynomial m*(n-2)*(n-3)*(n-4)*(n-5) is equal to zero at all the points {2, 3, 4, 5} on the number line.