2x^2+20x+42=0

解

2 x^{2} + 20 x + 42 = 0

x = - 3, x = - 7

解答ステップ

2 x^{2} + 20 x + 42 = 0

解くとthe二次式

x_{1, 2} = \frac{- 20 \pm 2 0 ^{2} - 4 \cdot 2 \cdot 42}{2 \cdot 2}

2 0^{2} - 4 \cdot 2 \cdot 42 = 8

x_{1, 2} = \frac{- 20 \pm 8}{2 \cdot 2}

解を分離する

x_{1} = \frac{- 20 + 8}{2 \cdot 2}, x_{2} = \frac{- 20 - 8}{2 \cdot 2}

x = \frac{- 20 + 8}{2 \cdot 2} : - 3

x = \frac{- 20 - 8}{2 \cdot 2} : - 7

二次equationの解:

x = - 3, x = - 7