Sort of in a hurry, so this may have mistakes in it, but here is my approach to the first: (Note that I assumed, as per the image, that 1>b>0)

Let P denote the rightmost side of the triangle A2 and Q denote the rightmost side of the triangle A1. Then:

but:

and:

So:

So we want to solve: w.r.t b. However, is strictly positive since therefore is obviously not an option. Now we get: