4x² -4x + 3 ≥ 0
4 · ( x² - x + 3 /4 ) = 4· [ x² -2·x · 1 /2 + 1/4 + 2/4] =
= 4 · [ x² - 2 ·x · 1/2 + ( 1/2 ) ² + 2 /4 ] =
trei termeni de binom
= 4 · [( x - 1/2)² + 2 /4] =
= 4 · ( x - 1 /2)² + 2 ≥ 0
↓
binom² =poz + 2 ≥ 0
daca x -1/2 =0 ; x =1/2 valoarea minima =2