展开 (X+Y=7,)(5X-2Y=-7)

解答

展开

(X + Y = 7,) (5 X - 2 Y = - 7)

5 XX - 2 X Y = - 7 X + Y = 7, 5 X - Y = 7, 2 Y = - Y = 7, 7

求解步骤

(X + Y = 7,) (5 X - 2 Y = - 7)

= (X + 7 =, Y) (5 X - 2 = Y - 7)

打开括号

X \cdot 5 X + X (- 2 Y =) + X (- 7) + Y = 7, 5 X + Y = 7, (- 2 Y =) + Y = 7, (- 7)

使用加减运算法则

+ (- a) = - a

5 XX - 2 X Y = - 7 X + Y = 7, 5 X - Y = 7, 2 Y = - Y = 7, 7

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