solvefor r,r^2+r-42=0

解

r, r^{2} + r - 42 = 0

r = 6, r = - 7

解答ステップ

r^{2} + r - 42 = 0

解くとthe二次式

r_{1, 2} = \frac{- 1 \pm 1 ^{2} - 4 \cdot 1 \cdot ( - 42 )}{2 \cdot 1}

1^{2} - 4 \cdot 1 \cdot (- 42) = 13

r_{1, 2} = \frac{- 1 \pm 13}{2 \cdot 1}

解を分離する

r_{1} = \frac{- 1 + 13}{2 \cdot 1}, r_{2} = \frac{- 1 - 13}{2 \cdot 1}

r = \frac{- 1 + 13}{2 \cdot 1} : 6

r = \frac{- 1 - 13}{2 \cdot 1} : - 7

二次equationの解:

r = 6, r = - 7