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Avijit Arya Grade: 12
        

I have got the answer of the question which satisfies the condition given, but its not actually the answer, the question is:-


log(ax) - 2log(x+1) = 0 . What is the value of a for which the above equation has exactly 1 root?


The answer which I got is 4. It satisfies the quadratic as well as log. But the teacher cut the whole marks. I dont know the answer, since it was the test paper of my friend and he had got no marks for getting 4. The question is of 8 marks, so it shouldnt be that easy. Please help me.

7 years ago

Answers : (1)

Badiuddin askIITians.ismu Expert
147 Points
										

Dear avijit


given


log(ax) - 2log(x+1) = 0


for this


ax>0   and x+1>0


 


lets solve


 log(ax) - 2log(x+1) = 0


or ax= (x+1)2


or x2 + x(2-a) +1=0


for unique solution discrimnent must be zero


 which give a=0 or 4


but ax>0 so a can't be zero


for a=4   x=1 is solution


which satisfy the given equation


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Badiuddin

7 years ago
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