Question

if x is equals to 5 minus root 21/2 so find x plus one upon x

Answer 1

Heya !!

X = ( 5 - ✓21 ) / 2

1/X = 2 / ( 5 - ✓21 )

1/X = 2 / ( 5 - ✓21 ) × ( 5 + ✓21 ) / ( 5 + ✓21 )

1/X = 2 ( 5 + ✓21 ) / ( 5 - ✓21 )( 5 + ✓21 )

1/X = 2 ( 5 + ✓21 ) / (5)² - (✓21 )²

1/X = 2 ( 5 + ✓21 ) / 25 - 21

1/X = 2 ( 5 + ✓21 ) 4 = 5 + ✓21 / 2

Therefore,

X + 1/X = ( 5 - ✓21 )/2 + ( 5 + ✓21 )/2

X + 1/X = ( 5 + ✓21 ) + ( 5-✓21) / 2

X + 1/X = ( 5 + 5 /2) = 10/2 = 5

Hence,

X + 1/X = 5.