bonjour
on rappelle (a+b)²=a²+2ab+b²
et (a+b) (c+d) = ac+ ad + bc+ bd
1)
E= (3x)² + 2*3x*2 + 2² - (5*3x + 5*2 - 2x*3x - 2x*2)
= 9x² + 12x + 4 - 15x - 10 + 6x² + 4x
= 15x² +x - 6
2) facteur comumn (3x+2)
E = (3x+2) [(3x+2) - (5-2x)]
= (3x+2) (5x - 3)
3) si x= - 2 alors E = (3*(-2) + 2) (5*(-2) -3) = -4 * (-13) = 52
ou = 15*(-2)² + (-2) - 6 = 60-2-6 = 52
