3x^2+21x+30=0

解

3 x^{2} + 21 x + 30 = 0

x = - 2, x = - 5

解答ステップ

3 x^{2} + 21 x + 30 = 0

解くとthe二次式

x_{1, 2} = \frac{- 21 \pm 2 1 ^{2} - 4 \cdot 3 \cdot 30}{2 \cdot 3}

2 1^{2} - 4 \cdot 3 \cdot 30 = 9

x_{1, 2} = \frac{- 21 \pm 9}{2 \cdot 3}

解を分離する

x_{1} = \frac{- 21 + 9}{2 \cdot 3}, x_{2} = \frac{- 21 - 9}{2 \cdot 3}

x = \frac{- 21 + 9}{2 \cdot 3} : - 2

x = \frac{- 21 - 9}{2 \cdot 3} : - 5

二次equationの解:

x = - 2, x = - 5