Help on OG11 question

[bha]

If X is an integer, is 9^x+9^-x=b?
1: 3^x+3^-x=sqrt(b+2)
2: x>0=b
OA is A
Stmt 1 is sufficient..we can deduce that by squaring both side of stmt1
what about stmt 2?...

[parallel_chase]

While posting the question pls check if you have posted the question correctly or not.

Kindly correct the statement II

This is OG 11 ques 142

9^x + 9^-x = b ?????

Statement I

3^x + 3^-x = sqrt(b+2)

3^x + 1/3^x = sqrt(b+2)

square both sides and expand

9^x + 1/9^x + 2 = b+2
9^x+1/9^x = b

Therefore sufficient.

Statement II

x>0

We dont know what b is, x could be anything 1,2,3,4,....n

Therefore Insufficient.

Hence A is the answer.

[bha]

Parallel_chase..thankks for ur prompt response.

In my book, stmt 2 says x>0=b..I verified it again....
but their answer explanation says - stmt 2 does't give any relationship between x and b....I guess it is typo error in question.

But if stmt is x=b..I think this stmt is sufficient as for any value of x>0, 9^x+9^-x will never be equal to x(=b)..hence stmt is sufficient...what do u think?

[parallel_chase]

Parallel_chase..thankks for ur prompt response.

In my book, stmt 2 says x>0=b..I verified it again....
but their answer explanation says - stmt 2 does't give any relationship between x and b....I guess it is typo error in question.

But if stmt is x=b..I think this stmt is sufficient as for any value of x>0, 9^x+9^-x will never be equal to x(=b)..hence stmt is sufficient...what do u think?

Yup there is a typo in your book

Statement II x>0

Thats why the explanation says no relationship between x and b