For the second question:
i. when x = 0, y = b
when y = 0, x = 4/b
Therefore letting A be the y intercept is (0,b) and B being the x intercept (4/b,0)
The x coordinate of P = (0+4/b) /2 = 2/b
The y coordinate of P = (0+b)/2 = b/2
Therefore P(2/b,b/2)
ii. y=1/x => subbing P in
L.H.S. = b/2...