1) = (3х - 6х²) +(-10ху +5у) = 3х(1 - 2х) -5у( 1 - 2у) = (1 -2у)(3х -5у)
2) = (21у - 35)+(6ху -10х) = 7(3у-5) -2х(3у -5) = (3у -5)(7 -2х)
3) = (35ab - 42ac) + (20b -24c) = 7a(5b - 6c) +4(5b - 6c) = (5b - 6c)(7a +4)
4) = (3x³ -21x²) + (4x -28) = 3x²(x -7) +4(x - 7) = (x -7)(3x² +4)
5) = (y³ +11y²) + (5y +55) = y²(y +11) + 5(y + 11)= (y + 11)(y² +5)
6) = (4x³ - 48 x²) + (5x -60) = 4x²(x -12) + 5(x - 12) = (x-12)(x² +5)