3u^2-21u=0

解

3 u^{2} - 21 u = 0

u = 7, u = 0

解答ステップ

3 u^{2} - 21 u = 0

解くとthe二次式

u_{1, 2} = \frac{- ( - 21 ) \pm ( - 21 ) ^{2} - 4 \cdot 3 \cdot 0}{2 \cdot 3}

(- 21)^{2} - 4 \cdot 3 \cdot 0 = 21

u_{1, 2} = \frac{- ( - 21 ) \pm 21}{2 \cdot 3}

解を分離する

u_{1} = \frac{- ( - 21 ) + 21}{2 \cdot 3}, u_{2} = \frac{- ( - 21 ) - 21}{2 \cdot 3}

u = \frac{- ( - 21 ) + 21}{2 \cdot 3} : 7

u = \frac{- ( - 21 ) - 21}{2 \cdot 3} : 0

二次equationの解:

u = 7, u = 0