Tìm x,y thuộc z :
Tìm x,y thuộc z :
b, ( x+1 ) . ( y+3 ) = 3
c, ( 2x-5 ) . ( y-3 ) = 13
d, ( x+2 ) . ( y-3 ) = -3
e, 1/x + 1/y = 1/8
f, 1/y + 1/x = 1/4
b, ( x+1 ) . ( y+3 ) = 3
c, ( 2x-5 ) . ( y-3 ) = 13
d, ( x+2 ) . ( y-3 ) = -3
e, 1/x + 1/y = 1/8
f, 1/y + 1/x = 1/4