Aptitude - Surds and Indices - Discussion

Discussion Forum : Surds and Indices - General Questions (Q.No. 15)
15.
If x = 3 + 22, then the value of x - 1 is:
x
1
2
22
33
Answer: Option
Explanation:

x - 1 2 = x + 1 - 2
x x

   = (3 + 22) + 1 - 2
(3 + 22)

   = (3 + 22) + 1 x (3 - 22) - 2
(3 + 22) (3 - 22)

   = (3 + 22) + (3 - 22) - 2

   = 4.

x - 1 = 2.
x

Discussion:
48 comments Page 3 of 5.

Ahmed said:   9 years ago
Actual answer is 4, but why should be 2.

Suma said:   9 years ago
Answer is 4 how do you get 2?

Vijay said:   9 years ago
Please explain how they take ^2over it?

Priyanka said:   9 years ago
Why -2 is wriiten at the end ? From where it came ?

Rohit said:   9 years ago
Answer is 4 how do you get 2?

Raja raviteja said:   9 years ago
^2 = 1.414.
3 + 2^2 = 5.828. Where ^x = ^5.818 = 2.414.

So, ^x - 1/^x = 2.414 - (1/2.414) = 2 =>answer.

Priyanka said:   9 years ago
Not getting this, can anyone explain clearly?

Harshini said:   9 years ago
In the 4th step, if you see the denominator: (a+b) (a-b) = (a^2-b^2) (using the formula).
It becomes 3^2 -(2 root 2)^2.
Which is 9 - (4 * 2),
=> 9 - 8 = 1.

Saurav Kumar said:   9 years ago
If x+1/x =1 then (x+1)^3 + 1/(x+1)^3 = ?

Please solve it.
(1)

Valens said:   9 years ago
How 4 = 2 at last?


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