x-1/x = 1/2, then the value of 4xsquare  + 4/x square (options) 7, -7, 9,-9, -8

Asked by Rony Joseph | 2nd Apr, 2014, 09:10: PM

Expert Answer:

Consider the given value of x minus 1 over x equals 1 half :
 
x minus 1 over x equals 1 half rightwards double arrow 2 cross times open parentheses x minus 1 over x close parentheses equals 2 over 2 rightwards double arrow 2 open parentheses x minus 1 over x close parentheses equals 1 N o w space c o n s i d e r space open parentheses 2 x minus 2 over x close parentheses squared : space open parentheses 2 x minus 2 over x close parentheses squared equals 4 x squared plus 4 over x squared minus 2 cross times 2 x cross times 2 over x rightwards double arrow open parentheses 2 x minus 2 over x close parentheses squared equals 4 x squared plus 4 over x squared minus 8 rightwards double arrow 1 squared equals 4 x squared plus 4 over x squared minus 8 rightwards double arrow 1 plus 8 equals 4 x squared plus 4 over x squared rightwards double arrow 4 x squared plus 4 over x squared equals 9
Thus the correct option is 9.

Answered by  | 3rd Apr, 2014, 09:00: AM

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