Latest elitmus Aptitude Question SOLUTION: log 2,log(2x-1),log(2x+3) are in ap then value of x is? a)log 5 base 2 b)1/2 c)not remmember d)log 2 base 5

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(#M40155126) ELITMUS Numerical Ability question elitmus Keep an EYE

log 2,log(2x-1),log(2x+3) are in ap then value of x is?
a)log 5 base 2 b)1/2 c)not remmember d)log 2 base 5

Asked In elitmus Gaurav kumar (8 years ago)

Unsolved Read Solution (7)

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NAVEEN KUMAR  (8 years ago)

Q. is absolutely right...
here is sol url---> http://postimg.org/image/442gpmi9l/

Is this solution Helpfull? Yes (22) | No   

NAVEEN KUMAR  (8 years ago)

Ans---5/2
In exam one was log 32 base 4 i.e 5/2

Is this solution Helpfull? Yes (8) | No   

RAHUL AGARWAL  (8 years ago)

I think Q is incorrect (2x nahi 2^x hoga)
If log 2 , log (2^x-1) , log ( 2^x+3) are in A.P
2 log (2^x-1)= log 2 + log (2^x+3)
log (2^x-1)^2 = log {2(2^x+3)} using this property ( log m + log n = log m/n)
cancel log both sides & let 2^x=y
(y-1)^2 = 2(y+3)
y^2+1-2y=2y+6
y^2-4y-5=0
y^2-5y+y-5=0
y(y-5)+1(y-5)=0
y=5 or y= -1
2^x=5 (2^x not equal to -1)
x= log 5 base 2 ( option a)

another sol. if Q is correct
acc. to Q
2log(2x-1)= log 2+ log (2x+3)
(2x-1)^2= 2(2x+3)
4x^2+1-4x=4x+6
4x^2-8x-5=0
4x^2-10x+2x-5
2x(2x-5)+1(2x-5)
(2x-5)(2x+1)
x=5/2 ( x not equal to -1/2)

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NAVEEN KUMAR  (8 years ago)

@ Mamta i hv alrdy mention the sol url in the Q...

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mamta kumari  (8 years ago)

plzz guys help me .I got confused .question is how many 5 digits can be formed by using 0,2,4,6,8 which is divisible by 8...i solved and i got answer 20.but this is not in option.,
the last 3 digit must be divisible by 8 so 024 can be arrannge in 2 ways only 024 and 240.but in others solution I saw they mentioned it arrange in 6 ways .I dont know how ..Plz make me understand yarr.If anone Know the correct method to solve it

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somnath  (8 years ago)

@Mamta mam....
1*2*3.....
3(240,248,024)
2(2 digit left)
1 digit left

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somnath  (8 years ago)

@Mamta mam....
1*2*3.....
3(240,248,024)
2(2 digit left)
1 digit left

Is this solution Helpfull? Yes | No (1)  

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