Archive
30th of March 2017
Mathematics
Q:

If x2 + 1/x2 = 51, find (i) x - 1/x (ii) x3 - 1/x3 ?

Nisha_vini29 - CBSE - Class IX

Thursday, March 30, 2017 at 16:01:PM

A:

G i v e n space x squared plus 1 over x squared equals 51 rightwards double arrow space x squared plus 1 over x squared equals 49 plus 2 rightwards double arrow space x squared plus 1 over x squared minus 2 equals 49 rightwards double arrow space open parentheses x minus 1 over x close parentheses squared equals 49 rightwards double arrow space open parentheses x minus 1 over x close parentheses squared equals 7 squared rightwards double arrow space open parentheses x minus 1 over x close parentheses equals 7 W e space k n o w space t h a t comma a cubed minus b cubed equals open parentheses a minus b close parentheses open parentheses a squared plus a b plus b squared close parentheses T h u s comma space x cubed minus 1 over x cubed equals open parentheses x minus 1 over x close parentheses open parentheses x squared plus x cross times 1 over x plus 1 over x squared close parentheses space space space space space space space space space space space space space equals open parentheses x minus 1 over x close parentheses open parentheses x squared plus 1 plus 1 over x squared close parentheses space space space space space space space space space space space space space space equals 7 cross times open parentheses 51 plus 1 close parentheses space space space space space space space space space space space space space equals 7 cross times open parentheses 52 close parentheses space space space space space space space space space space space space space equals 364

Thursday, March 30, 2017 at 16:08:PM