X2-3x+9/(х+3)(х2-3х+9) - х2+18/х2+27=х2-3х+9-х2-18/(х+3)х2-3х+9)=-9-3х(х+3)(х2-3х+9)=
=-3(х+3)/(х+3)(х2-3х+9)= 3/х2-3х+9
Верные равенства под первым и вторым номерами .
(2c + d - c - 2d )(2c + d + c + 2d) * 3cd =
= (c - d) (3c+3d) * 3cd = (c - d)(c + d)*9cd = (c²-d²)*9cd =
9c³d - 9cd³
А) (x-3)(x-7) -2x(3x-5)=x²-3x-7x+21-6x²+10x=-5x²+21=21-5x²
б) 4a(a-2)-(a-4)²=4a²-8a-(a²-8a+16)=4a²-8a-a²+8a-16=3a²-16
в) 2(m+1)²-4m=2(m²+2m+1)-4m=2m²+4m+2-4m=2m²+2
a) x³-9x=x(x²-9)=x(x-3)(x+3)
б) -5a²-10ab-5b²=-5(a²+2ab+b²)=-5(a+b)²
(y²-2y)²-y²(y+3)(y-3)+2y(2y²+5)=
=y⁴-4y³+4y²-y²(y²-9)+4y³+10y=
=y⁴-4y³+4y²-y⁴+9y²+4y³+10y=
=13y²+10y