Find critical number of the function 𝑓(𝑥)=11𝑥ln𝑥

Answer 1

y = 11x lnx
y' = 11(lnx + x/x) = 11 (lnx - 1)
so, where is y'=0 or y' is undefined?
y'=0 at x = e
y' is undefined at x <= 0