помогите плз очень необходимо даю 20б!

1. a) 5a(2 -a) +6a(a -7) =10a -5a +6a -42a =a -32a = a(a -32)

b) (b -3)(b -4) -(b +4) = b -4b -3b +12 -(b +8b +16) = b -7b+12-b-8b-16= -15b -4

в) 20x +5(x -2) =20x + 5(x -4x+4) =20x+5x-20x +20 =5x +20 =5(x +4)

2. a) 25y -y^3 =y(25 -y) = y(5 -y)(5 +y)

b) -4x +8xy -4y = -4(x - 2xy +y) = -4(x -y) = -4(x -y)(x -y)

1)5a(2-a)+6a(a-7)=10a-5a2+6a2-42a=a2-32a
   (b-3)(b-4)-(b+4)2=b2-3b-4b+12-(b2+8b+16)=
   =b2-7b+12-b2-8b-16=-15b-4
   20x+5(x-2)2=20x+5x2-20x+20=5x2+20
2)25y-y3=y(25-y2)=y(5+y)(5-y)
   -4x2+8xy-4y2=-4(x2-2xy+y2)=-4(x-y)2