bjr
a)
x² = 100
x² - 100 = 0
x² - 10² = 0 différence de deux carrés, on factorise
(x - 10)(x + 10) = 0 équation produit nul
(x - 10) = 0 ou (x + 10) = 0
x = 10 ou x = -10
S = {-10 ; 10}
b) x² = 15
x² - 15 = 0
x² - (√15)² = 0 on factorise et on continue comme au a)
c) -2x² + 19 = 7
2x² = 19 - 7
2x² = 12
x² = 6
x² - 6 = 0
x² - (√6)² = 0
.....
d) x² -5 = 0
x² - (√5)² = 0
......
e) x² -4x=0
x(x - 4) = 0
x = 0 ou x - 4 = 0
....
