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受欢迎的代数 >

4r^2+18r+13=-2

解答

4 r^{2} + 18 r + 13 = - 2

解答

r = \frac{- 9 + 21}{4}, r = - \frac{9 + 21}{4}

+1

十进制

r = - 1.10435 \dots, r = - 3.39564 \dots

求解步骤

4 r^{2} + 18 r + 13 = - 2

将

2

para o lado esquerdo

4 r^{2} + 18 r + 15 = 0

使用求根公式求解

r_{1, 2} = \frac{- 18 \pm 1 8 ^{2} - 4 \cdot 4 \cdot 15}{2 \cdot 4}

1 8^{2} - 4 \cdot 4 \cdot 15 = 221

r_{1, 2} = \frac{- 18 \pm 2 21}{2 \cdot 4}

将解分隔开

r_{1} = \frac{- 18 + 2 21}{2 \cdot 4}, r_{2} = \frac{- 18 - 2 21}{2 \cdot 4}

r = \frac{- 18 + 2 21}{2 \cdot 4} : \frac{- 9 + 21}{4}

r = \frac{- 18 - 2 21}{2 \cdot 4} : - \frac{9 + 21}{4}

二次方程组的解是:

r = \frac{- 9 + 21}{4}, r = - \frac{9 + 21}{4}

作图

流行的例子

-2x^2-40x-224=0

- 2 x^{2} - 40 x - 224 = 0

(3 x + 2) (x - 1) = 3 x

6 x^{2} + x + 1 = 0

2 k^{2} - 37 = 61

x^{2} - 7 = 9