Find the interval in which y=x2e−x is increasing.
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The function e^(−x) is always positive,
so you only need to look at x(2−x).
Figure out on what interval it is positive.
It is positive if the two factors are both positive or both negative.
But the first factor is negative only if x<0, and on that interval (2−x) is positive.
Next, notice that (2−x) is positive precisely if x<2.
dy/dx = 2x*e^(−x)−x²e^(−x) = 0
⇒x=0,2
f(x) is increasing in [ 0 , 2 ]
in (−∞,0] ∪ [2, ∞) f(x) is decreasing.......
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