Solve equation in interval

f = x^2*exp(-x)            % at interval x is <-1, 1>
fder = diff(f,x,1)

i need solution for fder in interval <-1 1>, but command solve(fder, [-1 1]) not work pls help

Answer 1

[Setsuna Yuuki.]

You can try:

syms x
f = x^2*exp(-x) 
fder = diff(f,x,1)
vpasolve(fder,[-1 1]) %change solve 

Answer 2

[Walter Roberson]

syms x
solve([diff(x^2*exp(-x)), x <= 1, x >= -1])

ans = 

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