Merci beacoup davance

A = (7x-1)² - (2x-3)²
   = (49x²-14x+1) - (4x²-12x+9)
   = 45x²-2x-8

B = (x²-18x+81) + (x-9)(2x-4)
    = (x-9)² + (x-9)(2x-4)
    = (x-9)(x-9) + (x-9)(2x-4)
    = (x-9)[(x-9)+(2x-4)]
    = (x-9)(3x-13)