Răspuns:
[tex]a) (x^{2} +3x-3x-9)(x^{2} +9)- x^{4} -4x^{2} -4 +3x^{2} -6x+3=[/tex]
= [tex](x^{2}-9)(x^{2} +9) -x^{4} -x^{2} -6x-1[/tex] =
[tex]x^{4} +9x^{2} -9x^{2} -81[/tex] [tex]- x^{4} -x^{2} -6x-1[/tex]= -[tex]x^{2}[/tex]-6x -82
b) [tex]x^{3} -x +5x^{2} -5 -x^{3} -8x^{2} -16x +x^{2} +2x+1=[/tex] -2[tex]x^{2}[/tex]-15x -4
c) [tex]9x^{2} y^{2} -15xy+15xy -25 - (9x^{2} y^{2} -12xy+4)=[/tex] 9[tex]x^{2} y^{2}[/tex] -25- 9[tex]x^{2} y^{2}[/tex]+12xy- 4=
12xy-29
d) (5x-8) (2x+2+ 3x+6) - (3x-4) ( 5x+10- 2x-6)= (5x-8) (5x+8) - (3x-4)(3x+4)=
25[tex]x^{2}[/tex]- 40x+40x- 64 - (9[tex]x^{2}[/tex] +12x-12x-16)= 25[tex]x^{2}[/tex] -64 - 9[tex]x^{2}[/tex] +16= 16[tex]x^{2}[/tex]-48 = 16([tex]x^{2}[/tex]-3)
