The 8th term of a linear sequence is 18 and 12th term is 26.find the first term,common difference and 20th term
18 = a + d(8-1)
26 = a + d(12-1)
18 = a + 7 d
26 = a + 11d
------------- subtract
-8 = - 4 d
so
d = 2
now go back and get a from either equation
Correct
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What about the common difference
The first term of a linear sequence is 3 and the 8th term is 31. Find the common difference
Tn= a+(n-1)d.
8th term= a+(n-1)d.
8thterm= a+(8-1)d.
term (8)=a+7d.
But a= 3.
So, 3+7d=31.
7d=31-3=7d=28(divide both sides) d= 4.