Wauw, I'm completely baffled by the questions on this site. Many of them are extremely basic.
The indifference curves (for u = 100 and depending on whether you express y as function of x or x as a function of y are):
As the MRS is the magnitude of the slope of the indifference curve we have that (see graph) when expressing x as a function of y that the slope of the indifference curve becomes much steeper as x becomes larger. Remember that x is on the second axis. This is in accordance with mrs(yx) = x. As x becomes larger (moving up along the second axis) the slope becomes steeper (or MRS becomes larger).
In the second example (which I think is much simpler) MRS(xy) = 1/x and as x becomes larger clearly the slope is going towards 0.