# Math Help - cdf

1. ## cdf

A random bariable X takes values between 0 and infinity with a CDF F(x)= A+B*exp(-x) for 0<=x<=oo.

Find values of A and B and graph cdf and what is P(2<=x<=3)?

2. The CDF of an exponential is $F(x)=1-e^{-x/\beta}$
so A=1, B=-1 and $\beta=1$. That probability is F(3)-F(2).

3. Originally Posted by bookie88
A random bariable X takes values between 0 and infinity with a CDF F(x)= A+B*exp(-x) for 0<=x<=oo.

Find values of A and B and graph cdf and what is P(2<=x<=3)?
To get the values of A and B note that you require $F(0) = 0$ and $F(+\infty) = 1$. Therefore ....