7b^2-14b-56=0

解

7 b^{2} - 14 b - 56 = 0

b = 4, b = - 2

解答ステップ

7 b^{2} - 14 b - 56 = 0

解くとthe二次式

b_{1, 2} = \frac{- ( - 14 ) \pm ( - 14 ) ^{2} - 4 \cdot 7 ( - 56 )}{2 \cdot 7}

(- 14)^{2} - 4 \cdot 7 (- 56) = 42

b_{1, 2} = \frac{- ( - 14 ) \pm 42}{2 \cdot 7}

解を分離する

b_{1} = \frac{- ( - 14 ) + 42}{2 \cdot 7}, b_{2} = \frac{- ( - 14 ) - 42}{2 \cdot 7}

b = \frac{- ( - 14 ) + 42}{2 \cdot 7} : 4

b = \frac{- ( - 14 ) - 42}{2 \cdot 7} : - 2

二次equationの解:

b = 4, b = - 2