展开-1(2x+y=7)

解答

展开

- 1 (2 x + y = 7)

- 2 x - y = 7

求解步骤

- 1 \cdot (2 x + y = 7)

= - 1 \cdot (2 x + 7 = y)

使用分配律:

a (b + c) = ab + a c

a = - 1, b = 2 x, c = y = 7

- 1 \cdot 2 x + (- 1) y = 7

使用加减运算法则

+ (- a) = - a

- 1 \cdot 2 x - 1 \cdot y = 7

乘开

- 1 \cdot 2 x - 1 \cdot y : - 2 x - y

- 2 x - y = 7

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