Salut,
[tex]Rela\c{t}iile\ lui\ Viete:\\\\x_1+x_2=-(-2)/1=2;\\x_1x_2=a/1=a;\\\\16=(x_1-x_2)^2=x_1^2-2x_1x_2+x_2^2=x_1^2+x_2^2-2x_1x_2=\\=(x_1+x_2)^2-2x_1x2-2x_1x_2=(x_1+x_2)^2-4x_1x_2\Rightarrow\\\Rightarrow 16=2^2-4a,\ deci\ a=-3.[/tex]
Simplu, nu ?
Green eyes.