The roots of the quadratic equation 2x2−6x+3=02x^2 - 6x + 3 = 0 are α\alpha and β\beta. Find the value of 1α+1β\frac{1}{\alpha} + \frac{1}{\beta}.

Worked solution

1. 利用韦达定理求出两根之和与两根之积

对于一元二次方程 2x2−6x+3=02x^2 - 6x + 3 = 0,各项系数分别为 a=2a = 2, b=−6b = -6, c=3c = 3。
由根与系数的关系(韦达定理)可得:
α+β=−ba=−−62=3\alpha + \beta = -\frac{b}{a} = -\frac{-6}{2} = 3
αβ=ca=32\alpha \beta = \frac{c}{a} = \frac{3}{2}

2. 将目标代数式通分,代入根与系数的值求出结果

将代数式 1α+1β\frac{1}{\alpha} + \frac{1}{\beta} 通分得:
1α+1β=α+βαβ\frac{1}{\alpha} + \frac{1}{\beta} = \frac{\alpha + \beta}{\alpha \beta}
代入 α+β=3\alpha + \beta = 3 和 αβ=32\alpha \beta = \frac{3}{2}:
1α+1β=332=3×23=2\frac{1}{\alpha} + \frac{1}{\beta} = \frac{3}{\frac{3}{2}} = 3 \times \frac{2}{3} = 2

Answer

2

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