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What is an arithmetic sequence whose common difference is -10?Was on my exam but still...
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An arithmetic sequence:
a1, a2, a3, a4,.....,an,..., where
a3=a2 + r= (a1 + r) + r= a1+ 2r
a4= a3 + r= a1 + 3r
an= a1 + (n-1)r
where r is the common difference
r = -10
a2= a1 + (-10)= a1 - 10
a3= a1 - 2X10
a4= a1 - 3X10
an= a1 - nX10
Posted by giorgiana1976 on January 26, 2009 at 5:25 PM (Answer #1)
Let's name the first term x1
So, the common difference is -10, lets name it c
So, the second term would be x1+c= x1+(-10)=x1-10
The third term would be x1+c+c= x1-10-10= x1-20
The forth term would be like x1+c+c+c= x1-10-10-10= x1-30
So, you might have guessed the nth term, which is:
nth term= x1+(n-1)*-10
The arthimetic sequence would be
x1, x1-10, x1-20, x1-30...... x1+(n-1)^-10.
Posted by revolution on July 24, 2010 at 11:18 PM (Answer #2)
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