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受欢迎的代数 >

3k^2-18k-21=0

解答

3 k^{2} - 18 k - 21 = 0

解答

k = 7, k = - 1

求解步骤

3 k^{2} - 18 k - 21 = 0

使用求根公式求解

k_{1, 2} = \frac{- ( - 18 ) \pm ( - 18 ) ^{2} - 4 \cdot 3 ( - 21 )}{2 \cdot 3}

(- 18)^{2} - 4 \cdot 3 (- 21) = 24

k_{1, 2} = \frac{- ( - 18 ) \pm 24}{2 \cdot 3}

将解分隔开

k_{1} = \frac{- ( - 18 ) + 24}{2 \cdot 3}, k_{2} = \frac{- ( - 18 ) - 24}{2 \cdot 3}

k = \frac{- ( - 18 ) + 24}{2 \cdot 3} : 7

k = \frac{- ( - 18 ) - 24}{2 \cdot 3} : - 1

二次方程组的解是:

k = 7, k = - 1

作图

流行的例子

x^{2} - x - 72 = 0

(10 x/6)(10 x/8)=10^{10}

(10 \frac{x}{6}) (10 \frac{x}{8}) = 1 0^{10}

-4(r+2)=4(2-2r)

- 4 (r + 2) = 4 (2 - 2 r)

3 x^{2} - 24 x + 36 = 0

(1-y)/7+y= y/2+3

\frac{1 - y}{7} + y = \frac{y}{2} + 3