Question

用带入方法解下列方程组1.y-7y=0,y+4x=15 2.x-y=3,x+y=5 3.2x+4y=5,x=1-y 4.

Answer 1

y-7y=0,∴y=0,x=15/4

x-y=3,∴x=y+3,代入x+y=5,得2y+3=5,∴y=1,再得出x=4

将x=1-y代入2x+4y=5,得2+2y=5,∴y=3/2,再得出x=-1/2

2x=5y,即x=5/2y,代入-x+3y=7,所以y=14,再得出x=35