Répondre :
( x + 5 ) ² - 16 ( x - 3 ) ²
=(x+5)²-(4(x-3))²
=(x+5)²-(4x-12)²
=(x+5+4x-12)(x+5-4x+12)
=(5x-7)(-3x+17)
=(x+5)²-(4(x-3))²
=(x+5)²-(4x-12)²
=(x+5+4x-12)(x+5-4x+12)
=(5x-7)(-3x+17)