Question 212504
sequence 4,7,10,....
formula 3n+1 
if two numbers of the sequence are multiplied need to show proof that result is always a number in this sequence. 
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You need to show that if two numbers having that form are multiplied
the product has that form.
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1st number 3a + 1
2nd number 3b + 1
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Product: 9ab + 3a + 3b + 1
Rearrange:
3(3ab+a+b) + 1
It has the form 3k+1
That proves what you were asked to prove.
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Cheers,
Stan H.
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