bjr
A = (x + 3) + (2x + 6)(x - 1) [ 2x + 6 = 2(x + 3) ]
= (x + 3)*1 + 2(x + 3)(x - 1) facteur commun (x + 3)
= (x + 3)*1 + 2(x + 3)(x - 1)
= (x + 3)[ 1 + 2(x - 1)
= (x + 3)(1 + 2x - 2)
= ( x + 3)(2x - 1)
B = 8x + 5x² + x
= 5x² + 8x + x
= 5x² + 9x
= x(5x + 9)
C = (4x + 1)(3x + 6) + (x + 2) [ 3x + 6 = 3(x + 2) ]
= (4x + 1)*3*(x + 2) + 1*(x + 2) facteur commun (x + 2)
= (4x + 1)*3*(x + 2) + 1*(x + 2)
= (x + 2) [3(4x + 1) + 1]
= (x + 2)(12x + 3 + 1)
= (x + 2)(12x + 4) [ 12x + 4 = 4(3x + 1) ]
= (x + 2)*4(3x + 1)
= 4(x + 2)(3x + 1)
