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The product of the first and the third terms of an arithmetic sequence is 9. If all terms of the sequence are positive integers, what is the fourth term?

 May 1, 2021
 #1
avatar+76 
+1

13 is the answer :)

 May 1, 2021
 #3
avatar+76 
+1

the answer is 13 because multiples of 9 are 1,3 and 9, so the first and third terms are 1 and 9

so the second term is 5, +4 is nine, +4 is 13

mathisopandcool  May 1, 2021
 #4
avatar+76 
+1

i still need to solve those problems but this is pretty fun to do :)

mathisopandcool  May 1, 2021
 #2
avatar+118611 
+1

1 , 5,  9 ,  13

 

Explanation  :    the  only two distinct  positive intergers  that  multiply to 9  are 1 and  9

 

The  second  integer  must  be  ( 1 + 9)  / 2  =  10 / 2  =   5

 

So.....the  common difference  is  4

 

cool cool cool

 May 1, 2021
edited by CPhill  May 1, 2021
edited by CPhill  May 1, 2021
 #5
avatar+76 
+1

o u did it a different way thats cool i didnt think of that :)

mathisopandcool  May 1, 2021
 #6
avatar+118611 
0

THX..  but......your  way  is just as  valid  as mine.....smiley smiley smiley

 

 

cool cool cool

CPhill  May 1, 2021

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