Function f (x) = x ^ 2 + 2x, the range of X ∈ [- 2,1] is? [] is bracket

Function f (x) = x ^ 2 + 2x, the range of X ∈ [- 2,1] is? [] is bracket

The vertex of F (x) is (- 1, - 1), obviously in the interval [- 2,1]
f(-2)=(-2)²+2(-2)=0
f(1)=1+2=3
By comparing the function values at the ordinate of the function vertex and the two end points, we can see that the maximum value of the function is 3 and the minimum value is - 1 at [- 2,1],
The value range is [- 1,3]