bonjour
trop long quand même , j'en fais 2
f (x) = x² - 4 x + 3
f (x) = ( x - 1 ) ( x - 3 ) = x² - 3 x - x + 3 = x² - 4 x + 3
f (x) = ( x - 2 )² - 1 = x² - 4 x + 4 - 1 = x² - 4 x + 3
f ( - 1 ) = ( - 1 )² - 4 *-1 + 3 = 1 + 4 + 3 = 8
f (x) = 0
( x - 1 ) ( x - 3 ) = 0
x = 1 ou 3
x² - 4 x + 3 = 3
x² - 4 x = 0
x ( x - 2 ) = 0
x = 0 ou 2
( x - 2 )² - 1 = 15
( x - 2 )² - 1 - 15 = 0
( x - 2 )² - 16 = 0
( x - 2 - 4 ) ( x - 2 + 4 ) = 0
( x - 6 ) ( x + 2 ) = 0
x = 6 ou - 2
( 1 + x ) / ( 5 + x ) = 3/5
5 + 5 x = 15 + 3 x
5 x - 3 x = 15 - 5
2 x = 10
x = 10/2 = 5
6/10 = 3/5
