If m is the A.M. of two distinct real numbers I and n(l, n > 1) and G1,G2 and G3 are three geometric means between l and n, then G41+2G42+G43 equals:
A
4lmn2
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B
4l2m2n2
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C
4l2mn
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D
4lm2n
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Solution
The correct option is D4lm2n m=l+n2 and common ratio of G.P. =r=(nl)14∴G1=l3/4n1/4,G2=l1/2n1/2,G3=l1/4n3/4G41+2G42+G43=l3n+2l2n2+ln3=ln(l+n)2=ln×2m2=4lm2n