quote:
Originally posted by somelauw
I solved them too by taking the formulas I know and then adjusting them to the ones similair by your sequences:
code:
1,3,6,10
y = (number/2) * (first + last)
y = (x/2)(x+1) = (x*x +x)/2
3, 6, 10, 15, 21
y = (x+1)(x+2)/2 = (x*x + 3x + 2)/2
1,2,4,8
y = g * x
y = 2 * (x - 1)
8, 16, 32, 64, 128
y = 2 * (x + 2)
Firstly, refer to
my post earlier in this thread.
Secondly, expression 1 is wrong. I mean the pattern you've considered isn't the one he wants...
The first expression is correct since its a standard. Its usually written as x*(x+1)/2
In the second expression, you are missing the condition where the first value (initial value) is to be taken as x=0; Your expression would be correct if you would have considered that.
(read my post for a complete explanation)
Third expression is horribly wrong. You've mixed up multiplication and exponentiation
Fourth expression is wrong because the series is the power of 2 series. You're multiplying 2 with numbers like 3,4,5,6 which won't give you the answers. What you needed was the raised to (also called exponential; noted as ^) and not the multiplication sign. If you replace the multiplication by exponentiation and consider the zero criteria (as mentioned in my post, your answer would be correct)
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