how do i find common difference if the first term is 3 and the seventh term is twice the third term. bit of help.
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Originally Posted by finnkeers how do i find common difference if the first term is 3 and the seventh term is twice the third term. bit of help. Hi finnkeers, Use Let Do a similar calculation using: Let Now set the two d's equal to each other and solve.
Last edited by masters; May 19th 2010 at 06:34 AM.
sorry but now i have two variables so how do i solve for d by getting rid of x
Originally Posted by finnkeers sorry but now i have two variables so how do i solve for d by getting rid of x Well, let's see. and Setting them equal to each other, we have If x = 6, then substituting into either equation with d, we get And there you have it!
first term (u1) = 3 u1 + 6d = 7th term But 7th term = 2(u1+2d) set equations equal to one another: 3 + 6d = 2(3+2d) 3+6d = 6+4d 6d-4d = 6-3 2d= 3 Therefore, d=3/2
thanks everyone. much appreciated.
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