If the sum of three consecutive terms of an AP is 51 and the product of first and third term is 273 find the third term .
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Solution
Let the three consecutive terms of AP be
a-d, a and a+d
Given
a-d+a+a+d= 51
3a=51
a=17 ...(1)
Also given that
(a-d)(a+d)=273
a2-d2=273
172-d2=273 (from (1))
289-d2=273
d2=16
d=4
So the third term is a+d= 17+4=21