[tex]\boxed{1.}~~~(y+3)(a+b)-(a+b)(1-2y)= \\ ~~~~~=(a+b)[(y+3)-(1-2y)]= \\ ~~~~~=(a+b)(y+3-1+2y)= \\ ~~~~~=(a+b)(3y+2).[/tex]
[tex]\boxed{2.}~~~3 x^{4}: x^{2} -2(x+3) ^{2} +(x+2y)(x-2y)+4 y^{2} -x(2x-14)= \\ =3 x^{2} -2( x^{2} +6x+9)+ x^{2} -4 y^{2} + 4y^{2} -2 x^{2} +14x= \\ =3 x^{2} -2 x^{2} -12x-18+ x^{2} - 2x^{2} +14x= \\ =2x-18.[/tex]
