y^2+21y=0

解

y^{2} + 21 y = 0

y = 0, y = - 21

解答ステップ

y^{2} + 21 y = 0

解くとthe二次式

y_{1, 2} = \frac{- 21 \pm 2 1 ^{2} - 4 \cdot 1 \cdot 0}{2 \cdot 1}

2 1^{2} - 4 \cdot 1 \cdot 0 = 21

y_{1, 2} = \frac{- 21 \pm 21}{2 \cdot 1}

解を分離する

y_{1} = \frac{- 21 + 21}{2 \cdot 1}, y_{2} = \frac{- 21 - 21}{2 \cdot 1}

y = \frac{- 21 + 21}{2 \cdot 1} : 0

y = \frac{- 21 - 21}{2 \cdot 1} : - 21

二次equationの解:

y = 0, y = - 21