I believe, while trying to compute dx and dy, you intended to find the elementwise product using the matrices of x and y. Try the following code instead with changes in lines 2 & 3.
dx = 3*(x-1).*y;
dy = 2-x-y.^2;
quiver(x, y, dx, dy, 'r', 'AutoScaleFactor', 2)
startx = -5:0.9:5;
starty = -2:0.6:5;
Modify the property ‘AutoScaleFactor’ to change the size of the arrows.
The code given above should produce the following output.