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CGP EDU Academic Team
Published on: August 13, 2026
The first term of an A.P. a 1 , a 2 , a 3 ,……, a n is unity. For what value of the common difference is a 1 a 3 + a 2 a 3 minimum?
Text Solution
Verified by ExpertsThe correct answer is:
CHECK THE SOLUTION.
Sol. Let the given A.P. be 1, 1 + d, 1 + 2d
a 1 a 3 + a 2 a 3 = (1 + 2d) + (1+3d+ 2d 2 ) = 2d 2 + 5d + 2
This will be min. at d = 
= – 
i.e. at vertex 
is minimum.
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