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受欢迎的代数 >

r^2-4r-91+7=0

解答

r^{2} - 4 r - 91 + 7 = 0

解答

r = 2 (1 + 22), r = 2 (1 - 22)

+1

十进制

r = 11.38083 \dots, r = - 7.38083 \dots

求解步骤

r^{2} - 4 r - 91 + 7 = 0

整理后得

r^{2} - 4 r - 84 = 0

使用求根公式求解

r_{1, 2} = \frac{- ( - 4 ) \pm ( - 4 ) ^{2} - 4 \cdot 1 \cdot ( - 84 )}{2 \cdot 1}

(- 4)^{2} - 4 \cdot 1 \cdot (- 84) = 422

r_{1, 2} = \frac{- ( - 4 ) \pm 4 22}{2 \cdot 1}

将解分隔开

r_{1} = \frac{- ( - 4 ) + 4 22}{2 \cdot 1}, r_{2} = \frac{- ( - 4 ) - 4 22}{2 \cdot 1}

r = \frac{- ( - 4 ) + 4 22}{2 \cdot 1} : 2 (1 + 22)

r = \frac{- ( - 4 ) - 4 22}{2 \cdot 1} : 2 (1 - 22)

二次方程组的解是:

r = 2 (1 + 22), r = 2 (1 - 22)

作图

流行的例子

completesquare 4x^2-28x+49

co m pl e t es q u a re 4 x^{2} - 28 x + 49

因式分解 m^2-5m-14=0

f a c t or m^{2} - 5 m - 14 = 0

5 n^{2} - 14 = - 6

2x^2+6x=sqrt(3)+x

2 x^{2} + 6 x = 3 + x

因式分解 x^2-x=6

f a c t or x^{2} - x = 6