d^2+d-72=0

解

d^{2} + d - 72 = 0

d = 8, d = - 9

解答ステップ

d^{2} + d - 72 = 0

解くとthe二次式

d_{1, 2} = \frac{- 1 \pm 1 ^{2} - 4 \cdot 1 \cdot ( - 72 )}{2 \cdot 1}

1^{2} - 4 \cdot 1 \cdot (- 72) = 17

d_{1, 2} = \frac{- 1 \pm 17}{2 \cdot 1}

解を分離する

d_{1} = \frac{- 1 + 17}{2 \cdot 1}, d_{2} = \frac{- 1 - 17}{2 \cdot 1}

d = \frac{- 1 + 17}{2 \cdot 1} : 8

d = \frac{- 1 - 17}{2 \cdot 1} : - 9

二次equationの解:

d = 8, d = - 9