1. a) 5a(2 -a) +6a(a -7) =10a -5a² +6a² -42a =a² -32a = a(a -32)
b) (b -3)(b -4) -(b +4)² = b² -4b -3b +12 -(b² +8b +16) = b² -7b+12-b²-8b-16= -15b -4
в) 20x +5(x -2)² =20x + 5(x² -4x+4) =20x+5x²-20x +20 =5x² +20 =5(x² +4)
2. a) 25y -y^3 =y(25 -y²) = y(5 -y)(5 +y)
b) -4x² +8xy -4y² = -4(x² - 2xy +y²) = -4(x -y)² = -4(x -y)(x -y)