5x-9y=7 2x-4y=3 解方程组
问题描述:
5x-9y=7 2x-4y=3 解方程组
答
5x-9y=7 (1)
2x-4y=3 (2)
(1)减去(2)× 2得
5x-9y - 2(2x-4y) = 7-2*3
化简得x - y = 1,即x = y+1,代入(2)式得
2(y+1) - 4y = 3
2y +2 - 4y = 3
解得y = -1/2
所以x = y+1 = 1/2