3x+2y=-1---(1)
2x+3y=6---(2)
From (1),y=-(3x+1)/2---(3)
Sub (3) into (2):
2x+3[-(3x+1)/2]=6
4x-3(3x+1)=12
4x-9x-3=12
-5x=15
x=-3---(4)
Sub (4) into (3):
y=-(3x+1)/2
=-[3(-3)+1]/2
=8/2
=4
Therefore x=-3,y=4
2007-03-06 17:25:03 補充:
If use 代入法:從(1)=2y=-1-3x y=-(1-3x)/2把(3)代(2):2x+ 3(-1-3x)/2=62x+3/2(-1-3x)=62x-3/2-9/2x-=612x-9-27x=3615x=-45x=-3把x=-3代入:y=[-1-3(-3)]/2 =[-1+9]/2 =4so I think用消元法恰當.