Given, x+1−2log2(3+2x)+2log4(10−2−x)=0
⇒x+1−2log2(3+2x)+2log22(2x10.2x−1)=0
⇒x+1−2log2(3+2x)+log2(2x10.2x−1)=0
⇒x+1−2log2(3+2x)+log2(10.2x−1)−log22x=0
⇒x+1−log2(3+2x)2+log2(10.2x−1)−xlog22=0
⇒x+1−log2(3+2x)2+log2(10.2x−1)−x=0
⇒x+1+log2[(3+2x)210.2x−1]−x=0
⇒1+log2[(3+2x)210.2x−1]=0
⇒log2[(3+2x)210.2x−1]=−1
⇒log2[9+(2x)2+6.2x10.2x−1]=log2(21)
⇒9+(2x)2+6.2x10.2x−1=21
⇒2(10.2x−1)=9+(2x)2+6.2x
⇒(2x)2−14.2x+11=0
Let 2x=y
⇒y2−14y+11=0
Let roots are {y}_{1}={2}^{{x}_{1}}&{y}_{2}={2}^{{x}_{2}}
Product of roots, y1y2=2x1×2x2=2x1+x2=11
⇒log2x1+x2=log11
⇒(x1+x2)log2=log11
⇒x1+x2=log2log11
Hence, x1+x2=log211
The sum of the roots of the equation, x+1-2 log_2(3+2^x)+2 log_4(10-2^-x)=0, is :
JEE Main 2021 — Mathematics Algebra
The sum of the roots of the equation, x+1−2log2(3+2x)+2log4(10−2−x)=0, is :
Held on 31 Aug 2021 · Verified 1 Jul 2026.
Options
- A
log214
- B
log212
- C
log213
- D
log211
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