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If log2,log(2x1),log(2x+3)\log 2, \log (2x - 1), \log (2x + 3) are in A.P, then xx is equal to ____

Solution

Correct Option: 1

When a,b,ca,b,c are in A.P, 2b=a+c2b=a+c

Hence,

2[log(2x1)]=log(2)+log(2x+3)2[log(2x-1)]=log(2)+log(2x+3)

We know that n.log(y)=log(y)nn.log(y)=log(y)^n and log(a)+log(b)=log(ab)log(a)+log(b)=log(ab)

So, log(2x1)2=log(4x+6)log(2x-1)^2=log(4x+6)

So, (2x1)2=4x+6(2x-1)^2=4x+6

4x2+14x=4x+64x^2+1-4x=4x+6

4x28x5=04x^2-8x-5=0

4x210x+2x5=04x^2-10x+2x-5=0

2x(2x5)+1(2x5)=02x(2x-5)+1(2x-5)=0

(2x+1)(2x5)=0(2x+1)(2x-5)=0

x=12x=-\frac{1}{2} or 52\frac{5}{2}

But log values are always positive, hence x=52x=\frac{5}{2}

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