Question

помогите решить 1номер и3

Answer 1

$1)\; \; 27x^3-y^3=(3x-y)(9x^2+3xy+y^2)\\25a^3-ab^2=a(25a^2-b^2)=a(5a-b)(5a+b)\\-3x^2-12x-12=-3(x^2+4x+4)=-3(x+2)^2\\3ab-15a+12b-60=3a(b-5)+12(b-5)=(b-5)(3a+12)\\a^4-625=(a^2-25)(a^2+25)=(a-5)(a+5)(a^2+25)\\\\3)\; a)\; \; 7m-n+49m^2-n^2=(7m-n)+(7m-n)(7m+n)=\\=(7m-n)(1+7m+n)\\\\b)\; \; 4x^2-4xy+y^2-16=(2x-y)^2-16=(2x-y-4)(2x-y+4)\\\\c)\; \; xy^4-2y^4-xy+2y=y^4(x-2)-y(x-2)=\\=(x-2)(y^4-y)=(x-2)\, y\, (y^3-1)=\\=(x-2)\, y\, (y-1)(y^2+y+1)\\\\d)\; \; 9-x^2-2xy-y^2=9-(x^2+2xy+y^2)=\\=9-(x+y)^2=(3-x-y)(3+x+y)$