If P (x, y) XY > 0, then p is in quadrant; if XY < 0, then p is in quadrant

If P (x, y) XY > 0, then p is in quadrant; if XY < 0, then p is in quadrant

When XY ＞ 0-3 quadrant, when XY ＜ 0-24 quadrant

The set M = {(x, y) | XY < 0, X ∈ R, y ∈ r} is ()
A. Point set in the first quadrant B. point set in the third quadrant C. point set in the fourth quadrant D. point set in the second and fourth quadrants

The set M = {(x, y) | XY ＜ 0, X ∈ R, y ∈ r} indicates that X and y are opposite numbers, so (x, y) are in the second and fourth quadrants. The set M = {(x, y) | XY ＜ 0, X ∈ R, y ∈ r} is the point set in the second and fourth quadrants

The coordinates of point a satisfy XY > 0, x + y

XY > 0, so x and y should have the same sign, which is satisfied in the first and third quadrants
2.x+y