a^2-2a-8=0

解

a^{2} - 2 a - 8 = 0

a = 4, a = - 2

解答ステップ

a^{2} - 2 a - 8 = 0

解くとthe二次式

a_{1, 2} = \frac{- ( - 2 ) \pm ( - 2 ) ^{2} - 4 \cdot 1 \cdot ( - 8 )}{2 \cdot 1}

(- 2)^{2} - 4 \cdot 1 \cdot (- 8) = 6

a_{1, 2} = \frac{- ( - 2 ) \pm 6}{2 \cdot 1}

解を分離する

a_{1} = \frac{- ( - 2 ) + 6}{2 \cdot 1}, a_{2} = \frac{- ( - 2 ) - 6}{2 \cdot 1}

a = \frac{- ( - 2 ) + 6}{2 \cdot 1} : 4

a = \frac{- ( - 2 ) - 6}{2 \cdot 1} : - 2

二次equationの解:

a = 4, a = - 2