(5-x)(-4-x)+18=0

解

(5 - x) (- 4 - x) + 18 = 0

x = 2, x = - 1

解答ステップ

(5 - x) (- 4 - x) + 18 = 0

拡張

(5 - x) (- 4 - x) + 18 : x^{2} - x - 2

x^{2} - x - 2 = 0

解くとthe二次式

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

(- 1)^{2} - 4 \cdot 1 \cdot (- 2) = 3

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

解を分離する

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

x = \frac{- ( - 1 ) + 3}{2 \cdot 1} : 2

x = \frac{- ( - 1 ) - 3}{2 \cdot 1} : - 1

二次equationの解:

x = 2, x = - 1