If a, b, c are in A.P. and a^2, b^2, c^2 are in G.P. such that a < b < c and a+b+c= 3 4, then the value of a is
JEE Main 2018 — Mathematics Algebra
2018mcqmedium
If a,b,c are in A.P. and a2,b2,c2 are in G.P. such that a<b<c and a+b+c=43, then the value of a is
Official previous-year question
Held on 15 Apr 2018 · Verified 6 Jul 2026.
Options
A
41−321
B
41−421
C
41−21
D
41−221
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Solution
∵a,b,c are in A.P. then a+c=2b also it is given that, a+b+c=43⇒2b+b=43⇒b=41 Again it is given that, a2,b2,c2 are in G.P. then (b2)2=a2c2⇒ac=±161 From (1), (2) and (3), we get; a±16a1=21⇒16a2−8a±1=0 Case I: 16a2−8a+1=0⇒a=41 (not possible as a<b) Case II: 16a2−8a−1=0⇒a=328±128⇒a=41±221∴a=41−221(∵a<b)
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