Q.

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 ________.          [2026]


Ans.

(2)

log(x+1)(2x2+5x+3)=4–log(2x+3)(x2+2x+1)

⇒ log(x+1)[(x+1)(2x+3)]=4–log(2x+3)[(x+1)(x+1)]

⇒ log(x+1)(x+1)|log(x+1)(2x+3)=4–log(2x+3)(x+1)2

⇒ log(x+1)(2x+3)=4–log(2x+3)(x+1)

⇒ log(x+1)(2x+3)+2log(2x+3)(x+1)–3=0

Let t=log(x+1)(2x+3), then log(2x+3)(x+1)=1t

⇒ t+2t–3=0

⇒ t2–3t+2=0 ⇒ (t–1)(t–2)=0

Case (i), t = 1;

log(x+1)(2x+3)=1

⇒ x+1=2x+3 ⇒ x=–2

For log(x+1),(x+1)>0

Let x + 1 = –1, which is invalid.

Case (ii), t = 2;

log(x+1)(2x+3)=2

⇒ x2+2x+1=2x+3 ⇒ x2=2

⇒ x=±2

⇒ x=2 (valid)

⇒ x=–2 (invalid)

∴ Sum of square of all real solution = (2)2=2