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受欢迎的代数 >

-r^2-25r+20=0

解答

- r^{2} - 25 r + 20 = 0

解答

r = - \frac{25 + 705}{2}, r = \frac{705 - 25}{2}

+1

十进制

r = - 25.77591 \dots, r = 0.77591 \dots

求解步骤

- r^{2} - 25 r + 20 = 0

使用求根公式求解

r_{1, 2} = \frac{- ( - 25 ) \pm ( - 25 ) ^{2} - 4 ( - 1 ) \cdot 20}{2 ( - 1 )}

(- 25)^{2} - 4 (- 1) \cdot 20 = 705

r_{1, 2} = \frac{- ( - 25 ) \pm 705}{2 ( - 1 )}

将解分隔开

r_{1} = \frac{- ( - 25 ) + 705}{2 ( - 1 )}, r_{2} = \frac{- ( - 25 ) - 705}{2 ( - 1 )}

r = \frac{- ( - 25 ) + 705}{2 ( - 1 )} : - \frac{25 + 705}{2}

r = \frac{- ( - 25 ) - 705}{2 ( - 1 )} : \frac{705 - 25}{2}

二次方程组的解是:

r = - \frac{25 + 705}{2}, r = \frac{705 - 25}{2}

作图

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