The equation of a curve is xy(x + y) = 2a3, where a is a non-zero constant. Show that there is only one point on the curve at which the tangent is parallel to the x-axis, and find the coordinates of this point.
I dont get how to do this/
You are told ' a' is a non-zero constant. So, if you want, you can think of 2a
3 as some number. When you differentiate a number like 10, for example, you simply get zero.
Hence :
x
2y + xy
2 = 2a
3Use the product rule for the left hand side terms and simply differentiate 2a
3 to get zero because, after all, its nothing but a number.