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受欢迎的代数 >

x^2-4x-15=18

解答

x^{2} - 4 x - 15 = 18

解答

x = 2 + 37, x = 2 - 37

+1

十进制

x = 8.08276 \dots, x = - 4.08276 \dots

求解步骤

x^{2} - 4 x - 15 = 18

将

18

para o lado esquerdo

x^{2} - 4 x - 33 = 0

使用求根公式求解

x_{1, 2} = \frac{- ( - 4 ) \pm ( - 4 ) ^{2} - 4 \cdot 1 \cdot ( - 33 )}{2 \cdot 1}

(- 4)^{2} - 4 \cdot 1 \cdot (- 33) = 237

x_{1, 2} = \frac{- ( - 4 ) \pm 2 37}{2 \cdot 1}

将解分隔开

x_{1} = \frac{- ( - 4 ) + 2 37}{2 \cdot 1}, x_{2} = \frac{- ( - 4 ) - 2 37}{2 \cdot 1}

x = \frac{- ( - 4 ) + 2 37}{2 \cdot 1} : 2 + 37

x = \frac{- ( - 4 ) - 2 37}{2 \cdot 1} : 2 - 37

二次方程组的解是:

x = 2 + 37, x = 2 - 37

作图

流行的例子

completesquare 9x^2-36+32

co m pl e t es q u a re 9 x^{2} - 36 + 32

18x^2-12mx+(6m-2)=0

18 x^{2} - 12 m x + (6 m - 2) = 0

b^{2} - 12 b - 9 = 8

solvefor x,3x^2-21x=0

so l v e f or x, 3 x^{2} - 21 x = 0

2 k (1) + k^{2} = 8