Question

If x +√15 = 4, then x+ 1/x =
A. 2
B. 4
C. 8
D. 1

Answer 1

Answer:

b is the correct answer

Answer 2

Given :  x + √15 = 4  

x = 4 - √15………..(1)

1/x = 1/(4 - √15)  

On rationalising the denominator :

1/x  = 1 × (4 + √15) / (4 - √15) × (4 + √15)  

1/x  = (4 + √15) / 4² - √15²  

1/x = (4 + √15) / 16 - 15

1/x = (4 + √15) / 1

1/x = 4 + √15 ……….(2)

Now, x + 1/x  

x + 1/x  = 4 - √15 + 4 + √15  

[From eq 1 and 2]

x + 1/x = 4 + 4

x + 1/x =  8

Hence the value of  x + 1/x is 8.

Among the given options option (C) 8 is correct.

HOPE THIS ANSWER WILL HELP YOU…..

 

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