x^2-21x+80=0

解

x^{2} - 21 x + 80 = 0

x = 16, x = 5

解答ステップ

x^{2} - 21 x + 80 = 0

解くとthe二次式

x_{1, 2} = \frac{- ( - 21 ) \pm ( - 21 ) ^{2} - 4 \cdot 1 \cdot 80}{2 \cdot 1}

(- 21)^{2} - 4 \cdot 1 \cdot 80 = 11

x_{1, 2} = \frac{- ( - 21 ) \pm 11}{2 \cdot 1}

解を分離する

x_{1} = \frac{- ( - 21 ) + 11}{2 \cdot 1}, x_{2} = \frac{- ( - 21 ) - 11}{2 \cdot 1}

x = \frac{- ( - 21 ) + 11}{2 \cdot 1} : 16

x = \frac{- ( - 21 ) - 11}{2 \cdot 1} : 5

二次equationの解:

x = 16, x = 5