Sagot :
Bonjour,
si tu as vu les identités remarquables :
(a+b)²=a²+2ab+b² donc (x+1)² = x²+2x+1
(a+b)(a-b)=a²-b² donc (x+5)(x-5) = x²-25
(a-b)²=a²-2ab+b² donc (4-x)² = x²-8x+16
si non :
(x+1)² = (x+1)(x+1) = x*x+x*1+1*x+1*1 = x²+x+x+1 = x²+2x+1
(x+5)(x-5) = x*x-x*5+5*x-5*5 = x²-5x+5x-25 = x²-25
(4-x)² = (4-x)(4-x) = 4*4-4*x-x-4-x*(-x) = 16-4x-4x+x² = x²-8x+16
