Ex. 1 :
A = 25x + 15 = 5(5x + 3)
B = 6x² + 5x = x(6x + 5)
C = 7(x+2)+3x(x+2) = (x+2)(3x + 7)
D = (5x + 6)² +(5x + 6)(2 - 3x)
= (5x+6)(5x+6)+(5x+6)(2-3x)
= (5x+6)[(5x+6)+(2-3x)]
= (5x+6)(5x-3x+6+2)
= (5x+6)(2x+8)
E = (7x-2)²-(7x-2)(2-3x)
= (7x-2)(7x-2)-(7x-2)(2-3x)
= (7x-2)[(7x-2)-(2-3x)]
= (7x-2)(7x-2-2+3x)
= (7x-2)(10x-4)
Ex. 2 :
a) 25 + 4x² + 20x = (5)² + (2x)² + 2 * 5 * 2x = (5 + 2x)²
b) 16y² + 49 + 56y = (4y)² + (7)² + 2 * 4y * 7 = (4y + 7)²
c) 6z + 9z² + 1 = 2 * 3z * 1 + (3z)² + (1)² = (3z + 1)²
tu essayes de faire le dernier ? (en sachant que : a² + 2ab + b² = (a + b)² )
