Verified answer

6

[tex]x(2-x)+x^{2} =4\\2x- x^{2} +x^{2} =4\\2x=4\\x=4:2\\x=2[/tex]

7

[tex]-(x-4)*(x+3)+x*(x+3)=3x-7\\(x+3)*(-x+4+x)=3x-7\\(x+3)*4=3x-7\\4x-12=3x-7\\4x-3x=-7-12\\x=-19[/tex]

8

[tex](x+3)(3-x)-x(2+x)+2x^{2} =9-x^{2} -2x-x^{2} +2x^{2} =9-2x[/tex]

Якщо х=-10

[tex]9-2*(-10)=9+20=29[/tex]