1.

If a, b, c are in G.P., prove that : (a2 + b2), (b2 + c2), (c2 + d2) are in G.P.

Answer»

a, b, c, d are in G.P. 

Therefore, 

bc = ad … (1) 

b2 = ac … (2) 

c2 = bd … (3) 

To prove: (a2 + b2), (b2 + c2), (c2 + d2) are in G.P, 

we need to prove that: 

(a2 + b2) (c2 + d2) = (b2 + c2)2 {deduced using GM relation} 

∴ RHS = (b2 + c2)2 = b4 + c4 + 2b2c2 

= a2c2 + b2d2 + a2d2 + b2c2 {using equation 2 and 3} 

= c2(a2 + b2) + d2(a2 + b2

= (a2 + b2) (c2 + d2) = LHS 

∴ (a2 + b2), (b2 + c2), (c2 + d2) are in G.P 

Hence proved.



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