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受欢迎的代数 >

-0.2(q-25)^2+165=-2q+140

解答

- 0.2 (q - 25)^{2} + 165 = - 2 q + 140

解答

q = 10, q = 50

求解步骤

- 0.2 (q - 25)^{2} + 165 = - 2 q + 140

在两边乘以

10

- 2 (q - 25)^{2} + 1650 = - 20 q + 1400

展开

- 2 (q - 25)^{2} + 1650 : - 2 q^{2} + 100 q + 400

- 2 q^{2} + 100 q + 400 = - 20 q + 1400

将

1400

para o lado esquerdo

- 2 q^{2} + 100 q - 1000 = - 20 q

将

20 q

para o lado esquerdo

- 2 q^{2} + 120 q - 1000 = 0

使用求根公式求解

q_{1, 2} = \frac{- 120 \pm 12 0 ^{2} - 4 ( - 2 ) ( - 1000 )}{2 ( - 2 )}

12 0^{2} - 4 (- 2) (- 1000) = 80

q_{1, 2} = \frac{- 120 \pm 80}{2 ( - 2 )}

将解分隔开

q_{1} = \frac{- 120 + 80}{2 ( - 2 )}, q_{2} = \frac{- 120 - 80}{2 ( - 2 )}

q = \frac{- 120 + 80}{2 ( - 2 )} : 10

q = \frac{- 120 - 80}{2 ( - 2 )} : 50

二次方程组的解是:

q = 10, q = 50

作图

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