CBSE Class 8 Answered

<div>1)Find the continued product:</div> <div>i) (x+1)(x-1)(x2+1)</div> <div>ii) (x-3)(x+3)(x2+9)</div> <div>2)If x + y = 12,find the value of (x2 + y2)</div> <div>3)if(x+1/x)=4,find the value of </div> <div>i)(x2 + 1/x2)</div> <div> </div>

Asked by feeroz | 08 May, 2016, 07:33: PM

Expert Answer

1. C o n s i d e r space t h e space g i v e n space e x p r e s s i o n colon open parentheses x plus 1 close parentheses open parentheses x minus 1 close parentheses open parentheses x squared plus 1 close parentheses W e space k n o w space t h a t space open parentheses a plus b close parentheses open parentheses a minus b close parentheses equals a squared minus b squared H e r e space a equals x space a n d space b equals 1 therefore open parentheses x plus 1 close parentheses open parentheses x minus 1 close parentheses equals x squared minus 1 squared equals x squared minus 1 therefore open parentheses x plus 1 close parentheses open parentheses x minus 1 close parentheses open parentheses x squared plus 1 close parentheses equals open parentheses x squared minus 1 close parentheses open parentheses x squared plus 1 close parentheses H e r e space a equals x squared space a n d space b equals 1 A g a i n space a p p l y i n g space t h e space s a m e space i d e n t i t y comma space w e space h a v e comma open parentheses x plus 1 close parentheses open parentheses x minus 1 close parentheses open parentheses x squared plus 1 close parentheses equals open parentheses open parentheses x squared close parentheses squared minus 1 squared close parentheses equals x to the power of 4 minus 1 2. G i v e n space t h a t space x plus y equals 12 space space space space space space... left parenthesis 1 right parenthesis W e space n e e d space t o space f i n d space t h e v a l u e space x squared plus y squared colon S q u a r i n g space t h e space e q u a t i o n space left parenthesis 1 right parenthesis space o n space b o t h space t h e space s i d e s comma space w e space h a v e comma open parentheses x plus y close parentheses squared equals 12 squared space space space space space space space space space... left parenthesis 2 right parenthesis W E space k n o w space t h a t space open parentheses a plus b close parentheses squared equals a squared plus 2 a b plus b squared H e r e comma space a equals x space a n d space b equals y T h e r e f o r e comma space open parentheses x plus y close parentheses squared equals x squared plus 2 x y plus y squared space space space space.. left parenthesis 3 right parenthesis T h u s comma space s u b s t i t u t i n g space t h e space v a l u e space o f space open parentheses x plus y close parentheses squared space f r o m space e q u a t i o n space left parenthesis 2 right parenthesis space i n space e q u a t i o n space left parenthesis 3 right parenthesis comma space w e space h a v e comma 12 squared equals x squared plus 2 x y plus y squared space rightwards double arrow x squared plus 2 x y plus y squared space equals 144 rightwards double arrow x squared plus y squared space equals 144 space minus 2 x y W i t h o u t space k n o w i n g space t h e space v a l u e space o f space x y comma space i t space w i l l space b e space d i f f i c u l t space t o space f i n d space t h e space v a l u e space o f space x squared plus y squared P l e a s e space c h e c k space t h e space q u e s t i o n 3. G i v e n space t h a t space open parentheses x plus 1 over x close parentheses equals 4 W E space n e e d space t o space f i n d space t h e space v a l u e space o f space x squared plus 1 over x squared colon W E space k n o w space t h a t space open parentheses a plus b close parentheses squared equals a squared plus 2 a b plus b squared C o n s i d e r space t h e space g i v e n space e q u a t i o n space open parentheses x plus 1 over x close parentheses equals 4 S q u a r i n g space b o t h space t h e space s i d e s comma space w e space h a v e comma open parentheses x plus 1 over x close parentheses squared equals 4 squared rightwards double arrow x squared plus 1 over x squared plus 2 x cross times 1 over x equals 16 space space space open square brackets a p p l y i n g space t h e space a b o v e space i d e n t i t y close square brackets rightwards double arrow x squared plus 1 over x squared plus 2 equals 16 rightwards double arrow x squared plus 1 over x squared equals 16 minus 2 rightwards double arrow x squared plus 1 over x squared equals 14

Answered by Vimala | 08 May, 2016, 10:15: PM

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