展开 (2x-5y=7,)(4x+2y=2)

解答

展开

(2 x - 5 y = 7,) (4 x + 2 y = 2)

8 x^{2} + 4 x y = 2

求解步骤

(2 x - 5 y = 7,) (4 x + 2 y = 2)

= (2 x - 5 \cdot 7 =, y) (4 x + 2 \cdot 2 = y)

使用 FOIL 方法:

(a + b) (c + d) = a c + a d + b c + b d

a = 2 x, b = - 5 y = 7,, c = 4 x, d = 2 y = 2

2 x \cdot 4 x + 2 x \cdot 2 y = 2 + (- 5 y = 7,) \cdot 4 x + (- 5 y = 7,) \cdot 2 y = 2

使用加减运算法则

+ (- a) = - a

2 \cdot 4 xx + 2 \cdot 2 x y = 2 - 5 y = 7, 4 x - 5 y = 7, 2 y = 2

乘开

2 \cdot 4 xx + 2 \cdot 2 x y : 8 x^{2} + 4 x y

8 x^{2} + 4 x y = 2

e x p an d 3 (3 x - 8 = 30)

e x p an d 9 cos (x y) (y + x \frac{d y}{d x})

e x p an d (5 x^{2} + x + 5) e^{x}

e x p an d \frac{15 ( x + 3 y ) - 2}{30 ( x + 3 y ) - 20}

e x p an d 21 + 18