Question

помогите плз очень нужно даю 20б!

Answer 1

1)5a(2-a)+6a(a-7)=10a-5aˇ2+6aˇ2-42a=aˇ2-32a
   (b-3)(b-4)-(b+4)ˇ2=bˇ2-3b-4b+12-(bˇ2+8b+16)=
   =bˇ2-7b+12-bˇ2-8b-16=-15b-4
   20x+5(x-2)ˇ2=20x+5xˇ2-20x+20=5xˇ2+20
2)25y-yˇ3=y(25-yˇ2)=y(5+y)(5-y)
   -4xˇ2+8xy-4yˇ2=-4(xˇ2-2xy+yˇ2)=-4(x-y)ˇ2

Answer 2

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)