3k^2-18k-21=0

解

3 k^{2} - 18 k - 21 = 0

k = 7, k = - 1

解答ステップ

3 k^{2} - 18 k - 21 = 0

解くとthe二次式

k_{1, 2} = \frac{- ( - 18 ) \pm ( - 18 ) ^{2} - 4 \cdot 3 ( - 21 )}{2 \cdot 3}

(- 18)^{2} - 4 \cdot 3 (- 21) = 24

k_{1, 2} = \frac{- ( - 18 ) \pm 24}{2 \cdot 3}

解を分離する

k_{1} = \frac{- ( - 18 ) + 24}{2 \cdot 3}, k_{2} = \frac{- ( - 18 ) - 24}{2 \cdot 3}

k = \frac{- ( - 18 ) + 24}{2 \cdot 3} : 7

k = \frac{- ( - 18 ) - 24}{2 \cdot 3} : - 1

二次equationの解:

k = 7, k = - 1