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受欢迎的代数 >

100=20t+1/2 0.2t^2

解答

100 = 20 t + \frac{1}{2} 0.2 t^{2}

解答

t = 10 (110 - 10), t = - 10 (10 + 110)

+1

十进制

t = 4.88088 \dots, t = - 204.88088 \dots

求解步骤

100 = 20 t + \frac{1}{2} \cdot 0.2 t^{2}

在两边乘以

10

1000 = 200 t + t^{2}

交换两边

200 t + t^{2} = 1000

将

1000

para o lado esquerdo

200 t + t^{2} - 1000 = 0

改写成标准形式

a x^{2} + b x + c = 0

t^{2} + 200 t - 1000 = 0

使用求根公式求解

t_{1, 2} = \frac{- 200 \pm 20 0 ^{2} - 4 \cdot 1 \cdot ( - 1000 )}{2 \cdot 1}

20 0^{2} - 4 \cdot 1 \cdot (- 1000) = 20110

t_{1, 2} = \frac{- 200 \pm 20 110}{2 \cdot 1}

将解分隔开

t_{1} = \frac{- 200 + 20 110}{2 \cdot 1}, t_{2} = \frac{- 200 - 20 110}{2 \cdot 1}

t = \frac{- 200 + 20 110}{2 \cdot 1} : 10 (110 - 10)

t = \frac{- 200 - 20 110}{2 \cdot 1} : - 10 (10 + 110)

二次方程组的解是:

t = 10 (110 - 10), t = - 10 (10 + 110)

作图

流行的例子

7 x^{2} + 7 = 0

5 x^{2} - 6 = - x

3 x^{2} - 96 x - 92 = 0

completesquare x^2+20x+5

co m pl e t es q u a re x^{2} + 20 x + 5

x (400 - x) = 10000