bonjour
1. A = 1 - 2 / ( x + 1 )
A = [1 ( x + 1 ) / ( x + 1 ) - 2 / ( x + 1 )
A = ( x + 1 - 2 ) / ( x + 1 )
A = ( x - 1 ) / ( x + 1 )
A = 2 x / x + 1 ) - 1
= ( 2 x / x + 1 ) - 1 ( x + 1 ) / ( x + 1 )
= ( 2 x - x - 1 ) / ( x + 1 )
= ( x - 1 ) / ( x +1 )
pour x = √ 3
A = ( √3 - 1 ) / ( √3 + 1 )
= ( √3 - 1 ) ( √3 + 1 ) / ( √3 + 1 ) ( √3 - 1 )
= ( 3 - 1 ) / ( 3 - 1 )
= 2 /2 = 1
A = 0 avec x ≠ - 1
x - 1 = 0 ⇔ x = 1