聯立方程和因式分解

以代入法解以下聯立方程
3x+5y=7 ----------(1)
5x-3y=6 -------------(2)

(1)*3 + (2)*5, 34x = 51 => x = 3/2
Sub x = 3/2 into (2),
15/2 - 3y = 6 => y = -1/2

因式分解下列式
6(a-1)^2+2a(a-1)
= [6(a-1)+2a](a-1)
= (6a-6+2a)(a-1)
= (8a -6)(a-1)
= 2(4a-3)(a-1)


2011-06-27 14:08:44 補充：
Oops...
15/2 - 3y = 6
15/2 - 12/2 = 3y
3/2 = 3y
y = 1/2

The value of y in the first part is incorrect.

x = 3/2

From (2),
5(3/2) - 3y = 6
15/2 - 3y = 6
3y = 15/2 - 6
= 3/2
y = 1/2