What is the probability of $P(X+Y=1)$?

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$X$~$Exp(1.4)$ and $Y$~$Exp(2.8)$ are independent. What is the probability of $P(X+Y=1)$. I've tried to use the convolution theorem but I couldn't figure it out.

Thank you for your help in advance

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Assuming you are meant to be working with exponential and not Poisson random variables, the sum of two independent exponential random variables is distributed according to the Gamma distribution (see https://en.wikipedia.org/wiki/Exponential_distribution). Note that since you have a continuous distribution the probability of hitting any one point is 0.

For this reason I will mention the Poisson case. The sum of Poisson random variables is again Poisson with parameter being the sum of parameters (in this case $1.4+2.8=4.2$). You can then use the known formula for a Poisson random variable to find the solution.