Question

tim x; y biết 3xy+y=4-x

 

Answer 1

<=>(3x+1)y=4-x

=>(3x+1)y-(-x)-4=0

=>(3x+1)y+x-4=0

*)3x+1=0                             *)3y+1=0

=>3x=-1                                 =>3y=-1

=>x=\(-\frac{1}{3}\)                             =>y=\(-\frac{1}{3}\)

Answer 2

Ta có :3xy+y+x=4

=>3(3xy+y+x)=4*3

=>9xy+3y+3x=12

=>(3x+1)(3y+1)=13

Ta có bảng

3x+1	13	1	-1	-13
3y+1	1	13	-13	-1
x	4	0	-2/3	-14/3
y	0	4	-14/3	-2/3