Calculas help plz max and min

fina all relative extreme ( max and min or neither )

y = -3x^5 + 5x^3

so what i did is :

y' = -15x^4 + 15x^2

-15x^2 (x^2-1) = 0

x= 0 , x= 1 , x=-1

whats next ???

correct you got the value of x = 1 ok

then do f ' x = d^2y/dx^2

-15x^4+15x^

then f ' x -15x4= -60

then = -60x^3+30x

you have the value of x then substitute

-60(1)^3+30(1) = -30

so it is a max point