✔ 最佳答案
Quadratic Equation:
x² - 3x + 7 = 0
a = 1, b = -3, c = 7
x = [-b ± √(b² - 4ac)]/2a
x = [-(-3) ± √((-3)² - 4(1)(7))]/2(1)
x = [3 ± √(9 - 28)]/2
x = [3 ± √(-19)]/2
x = [3 ± √(-1*19)]/2
x = (3 ± √-1√19)/2
x = (3 ± i√19)/2
x = (3 + i√19)/2 = 1.5 + 2.1794i
x = (3 - i√19)/2 = 1.5 - 2.1794i
Completing the Square:
x² - 3x + 7 = 0
x² - 3x = -7
x² - 3x + (9/4) = -7 + (9/4)
(x - (3/2))(x - (3/2)) = (-28/4) + (9/4)
(x - (3/2))² = -19/4
x - (3/2) = ±√(-19/4)
x - (3/2) = ±(√-19)/√4
x - (3/2) = ±(√-1*19)/2
x - (3/2) = ±(i√19)/2
x = (3/2) ± (i√19)/2
x = (3 ± i√19)/2
x = (3 + i√19)/2 = 1.5 + 2.1794i
x = (3 - i√19)/2 = 1.5 - 2.1794i