Question

用代入法解方程组x-y=3，3x-8y=4，由x-y=3得

Answer 1

由x-y=3得，x=y+3，代入3x-8y=4，得3(y+3)-8y=45y=5y=1x=y+3=4

Answer 2

由x-y=3得x=3+y带入3x-8y=49+3y-8y=45y=5y=1y=1带入x=3+y得x=4

Answer 3

x-y=3，3x-8y=4，由x-y=3得 x = y + 3==> 3 * (y +3) - 8y = 4==> 3y + 9 - 8y = 4==> -5y = -5==> y = 1 x = y + 3 = 1 + 3 = 4 x = 4y = 1