1) =x²+2x+5x+10=x(x+2)+5(x+2)=(x+5)(x+2)
2) un tetraedru are 6 muchii, 180:6=30 cm latura
3)=[tex] \frac{x^2(x+1)-9(x+1)}{x^2(x-3)-(x-3)}= \frac{(x^2-9)(x+1)}{(x^2-1)(x-3)}= \frac{(x-3)(x+3)(x+1)}{(x^2-1)(x-3)}(simpl.cu(x-3))= [/tex]
[tex]= \frac{(x+3)(x+1)}{x^2-1} [/tex]