Odpowiedź:
1.
[tex](-x-y)(2x+3y)=-2x^{2} -3xy-2xy-3y^{2} =\\ =-2x^{2} -3y^{2} -5xy[/tex]
2.
[tex](3x-5y)(-x+y)=-3x^{2} +3xy+5xy-5y^{2} =\\ =-3x^{2} -5y^{2} +8xy\\ \\ x=-3\\ -3x^{2} -5y^{2} +8xy=-3*(-3)^{2} -5y^{2} +8*(-3)*y=\\ =-3*9-5y^{2} -24y=-5y^{2} -24y-27[/tex]
3.
[tex]2(a+b)-(a-2b)(2a+b)+3(2a+3b)=\\ =2a+2b-(2a^{2} +ab-4ab-2b^{2} )+6a+9b=\\ =2a+2b-2a^{2} +3ab+2b^{2} +6a+9b=\\ =-2a^{2} +2b^{2} +3ab+8a+11b[/tex]
4.
[tex]3(x+y)-(2x+y)(x-3y)+3(2x+3y)=\\ =3x+3y-(2x^{2} -6xy+xy-3y^{2} )+6x+9y=\\ =9x+11y-2x^{2} +5xy+3y^{2} \\ \\ x=-2\\ 9x+11y-2x^{2} +5xy+3y^{2}=\\ =9*(-2)+11y-2*(-2)^{2} +5*(-2)*y+3y^{2} =\\ =-18+11y-8-10y+3y^{2} =3y^{2} +y-26[/tex]
5.
[tex]-2(x-3)(x+3)-3x(x-2)-2(x-3x)^{2} =\\ =-2(x^{2} -9)-3x^{2} +6x-2(-2x)^{2} =\\ =-2x^{2} +18-3x^{2} +6x-2*4x^{2} =\\ =-x^{2} +6x-8x^{2} +18=-7x^{2} +6x+18[/tex]
6.
[tex]-3(x+1)(x-2)=-3(x^{2} -2x+x-2)=\\ =-3(x^{2} -x-2)=-3x^{2} +3x+6\\ \\ x=\frac{1}{3}\\ -3x^{2} +3x+6=-3*(\frac{1}{3})^{2} +3*\frac{1}{3}+6=\\ =-3*\frac{1}{9} +1+6=-\frac{1}{3}+7=6\frac{2}{3}[/tex]
7.
[tex](3x-2)^{2} =9x^{2} -12x+4[/tex]
