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受欢迎的代数 >

(7x-5)(3x+8)=15x+12

解答

(7 x - 5) (3 x + 8) = 15 x + 12

解答

x = \frac{- 13 + 1261}{21}, x = - \frac{13 + 1261}{21}

+1

十进制

x = 1.07193 \dots, x = - 2.31002 \dots

求解步骤

(7 x - 5) (3 x + 8) = 15 x + 12

展开

(7 x - 5) (3 x + 8) : 21 x^{2} + 41 x - 40

21 x^{2} + 41 x - 40 = 15 x + 12

将

12

para o lado esquerdo

21 x^{2} + 41 x - 52 = 15 x

将

15 x

para o lado esquerdo

21 x^{2} + 26 x - 52 = 0

使用求根公式求解

x_{1, 2} = \frac{- 26 \pm 2 6 ^{2} - 4 \cdot 21 ( - 52 )}{2 \cdot 21}

2 6^{2} - 4 \cdot 21 (- 52) = 21261

x_{1, 2} = \frac{- 26 \pm 2 1261}{2 \cdot 21}

将解分隔开

x_{1} = \frac{- 26 + 2 1261}{2 \cdot 21}, x_{2} = \frac{- 26 - 2 1261}{2 \cdot 21}

x = \frac{- 26 + 2 1261}{2 \cdot 21} : \frac{- 13 + 1261}{21}

x = \frac{- 26 - 2 1261}{2 \cdot 21} : - \frac{13 + 1261}{21}

二次方程组的解是:

x = \frac{- 13 + 1261}{21}, x = - \frac{13 + 1261}{21}

作图

流行的例子

x^{2} + 42 x = 0

13 x^{2} - 7 = 62

solvefor y,x^2+y^2=81

so l v e f or y, x^{2} + y^{2} = 81

8^{2} + b^{2} = 9^{2}

2 y^{2} + y - 2 = 0