Ca o ecuatie de gradul 2 sa aiba radacinile egale punem conditia ca delta sa fie egala cu 0.
○ 4x²+mx+9 = 0
Delta = m²-4*4*9 = m²-144
=> m²-144 = 0
m² = 144
m = +/- 12
○ mx²+4x+1 = 0
Delta = 16 - 4*m*1 = 16-4m
=> 16-4m = 0
-4m = - 16
m = 4
○ x²-2(1+3m)x+7(3-2m) = 0
x²+(-2-6m)x + (21-14m) = 0
Delta = (2-6m)² - 4*1*(21-14m) = 4 - 24m + 36m² - 84 + 56m = 36m²+80m-80
=> 36m²-32m-80 = 0 | :4
9m²+20m-20 = 0
Delta = 400-4*9*(-20) = 1120
m1 = (-20 + 4√70)/18 = (-10+2√70)/9
m2 = (-20-4√70)/18 = (-10-2√70)/9
