3x^2-18x-81=0

解

3 x^{2} - 18 x - 81 = 0

x = 9, x = - 3

解答ステップ

3 x^{2} - 18 x - 81 = 0

解くとthe二次式

x_{1, 2} = \frac{- ( - 18 ) \pm ( - 18 ) ^{2} - 4 \cdot 3 ( - 81 )}{2 \cdot 3}

(- 18)^{2} - 4 \cdot 3 (- 81) = 36

x_{1, 2} = \frac{- ( - 18 ) \pm 36}{2 \cdot 3}

解を分離する

x_{1} = \frac{- ( - 18 ) + 36}{2 \cdot 3}, x_{2} = \frac{- ( - 18 ) - 36}{2 \cdot 3}

x = \frac{- ( - 18 ) + 36}{2 \cdot 3} : 9

x = \frac{- ( - 18 ) - 36}{2 \cdot 3} : - 3

二次equationの解:

x = 9, x = - 3