The sum of squares of all the real solutions of the equation log_(x+1)(2x^2+5x+3) = 4 - log_(2x+3)(x^2+2x+1) is equal to .
JEE Main 2026 — Mathematics Algebra
2026integermedium
The sum of squares of all the real solutions of the equation log(x+1)(2x2+5x+3)=4−log(2x+3)(x2+2x+1) is equal to ________.
Official previous-year question
Held on 8 Apr 2026 · Verified 1 Jul 2026.
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Solution
For the logarithms to be defined, we must satisfy the following conditions: 1. Base of the first logarithm: x+1>0⇒x>−1 and x+1=1⇒x=0. 2. Base of the second logarithm: 2x+3>0⇒x>−23 and 2x+3=1⇒x=−1. 3. Arguments must be positive: 2x2+5x+3>0 and x2+2x+1>0. Taking the intersection of all these conditions, the domain of the equation is x∈(−1,0)∪(0,∞). Now, factorizing the arguments of the logarithms: 2x2+5x+3=(2x+3)(x+1) x2+2x+1=(x+1)2 Substitute these into the given equation: log(x+1)((2x+3)(x+1))=4−log(2x+3)((x+1)2) Using the properties of logarithms: log(x+1)(2x+3)+log(x+1)(x+1)=4−2log(2x+3)(x+1) log(x+1)(2x+3)+1=4−log(x+1)(2x+3)2 Let t=log(x+1)(2x+3). The equation becomes: t+1=4−t2 t−3+t2=0 t2−3t+2=0 (t−1)(t−2)=0 ⇒t=1 or t=2 Case 1: t=1 log(x+1)(2x+3)=1 2x+3=x+1 x=−2 This value is rejected because x=−2 does not fall in the domain x>−1. Case 2: t=2 log(x+1)(2x+3)=2 2x+3=(x+1)2 2x+3=x2+2x+1 x2=2 x=±2 Since x>−1, x=−2 is rejected. The only valid solution is x=2. The sum of squares of all the real solutions is (2)2=2. Answer: 2
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