(1)2x^2+6xy-10y
=2(x²+3xy-5y)
(2)4x^3-12x^2-18x
=2x(x²-6x-9)
(3)-7ab-14abx+49aby
=-7ab(1+2x-7y)
(4)5x(a+b-c)-10y(a+b-c)
=5(a+b-c)(x-2y)
(5)πR^2-4πr^2
=π(R²-4r²)
=π(R+2r)(R-2r)