Devoir de factorisation

bonsoir

a = ( x + 7 + 6) ( x + 7 - 6) 
a = ( x + 13) ( x + 1)

b = ( 2 x + 2)²

c = ( x + 1) ( x  +13 - 4 ( x + 1)
c = ( x + 1) ( x + 13 - 4 x - 4)
c = ( x +1) ( - 3 x + 9)