Most Important Selected Qs for JEE AdvancedMathematicsSequences and Series

The sum of the first three numbers in an A.P. is 24 and their product is 384. Then which of the following hold(s) good?

Options

Asum of n terms can be 2n(n + 1)
Bsum to n terms can be 2n(n + 3)
Csum of n terms can be 14 n-2 n^2
Dsum of the squares of the three numbers is 224

Correct answer

D. sum of the squares of the three numbers is 224

Step-by-step solution

Let the number be (a-d), a,(a+d)3 a=24a=8 Also (8-d)(8)(8+d)=384 aligned & d^2=16 & d=4 or -4 aligned Hence series is 4,8,12, . aligned & S_n=2 n(n+1) or 12,8,4, & S_n=14 n-2 n^2 aligned

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