ax² + bx + c = 0
D = b² - 4ac
x(1,2) = ( -b +/- √D)/2a
Например:
x² - 8x + 15 = 0
( a = 1, b = -8, c = 15)
D = (-8)² - 4*1*15 = 64 - 60 = 4 = 2²
x(1) = ( -(-8) + √4 )/2 = ( 8 + 2 )/2 = 10/2 = 5
x(2) = ( -(-8) - √4 )/2 = ( 8 - 2 )/2 = 6/2 = 3
