Hi there,
Just a quick question, I am slightly confused as to the mark scheme for this question:
(b) The continuous random variable Y takes values between 1 and 2 and its cumulative distribution function F is given, for 1 < y < 2, by
F(y ) = ay + by^2.
Find the values of the constants a and b.
Now I understand to input F(1) into it so I get a+b=0 (like what the mark scheme says) and then F(2) so 2a+4b.. but then it equals this second equation to 1 for some reason?
I know how to find a and b after getting the two equations but I just wanted to know why that second equation equals 1?