Bonsoir ,
a)
9 - 12x + 4x²
= 3² - 2 × 3 × 2x + (2x)²
= (3-2x)²
b)
(3-2x)² - 4
= (3-2x)² - 2²
= [ (3-2x) - 2 ] [ (3-2x) + 2 ]
= (1-2x) (5-2x)
c)
E = (3-2x)² - 4
E = (1-2x) (5-2x)
d)
(1-2x) (5-2x) = 0
1 - 2x = 0 ou 5 - 2x = 0
-2x = -1 -2x = -5
x = -1/-2 x = -5/-2
x = 1/2 x = 5/2
e)
- pour x = 3/2 :
E = (1-2x) (5-2x)
E = (1-2(3/2) ) (5-2(3/2) )
E = ( 1 - 6/2) (5-6/2)
E = (1-3) (5-3)
E = -2 × 2
E = -4
-4 ∈ Z .