y=3+e^-x
at x=0, e^0=1, so y=4
at x=1, e^-1=1/e=1/2.718281828459045=0.367879441, add 3 & y=3.367879
at x=2, e^-2=1/(e*e)=1/7.389056096=0.135335283, so y=3.135335283
for bigger x, yu get 1/(e tu bigger powers), so this tem approach zero
so y get kloes tu 3 as x get big