Take the derivative of f(x), set it to zero, and solve for x. Those x values will be the extreme values:
f(x) = x2 + 3x-1 + 1
df(x)/dx = 2x - 3x-2
0 = 2x - 3x-2
3/x2 = 2x
3/2 = x3
(3/2)1/3 = x
You try the second one. Change the sqrt to a power of 1/2: sqrt(1-x2) = (1-x2)1/2. Apply the Chain Rule.