5x^2-12x+1=0
x1,x2-корнi
B=x1^2+x2^2-x1x2
Теорема Вiета:x1+x2=12
x1.x2=1
(x1+x2)^2=x1^2+x2^2+2x1.x2
x1^2+x2^2=(x1+x2)^2-2x1.x2=12^2-2.1=144-2=142
5x^2-12x+1=0
x1,x2-корнi
B=x1^2+x2^2-x1x2
Теорема Вiета:x1+x2=12
x1.x2=1
(x1+x2)^2=x1^2+x2^2+2x1.x2
x1^2+x2^2=(x1+x2)^2-2x1.x2=12^2-2.1=144-2=142