Calculus help please?!?!? (abs max and min values??)

1) Find the absolute maximum and absolute minimum values of f(x) = √(9 − x^2) on interval [−1, 2]

(a) abs. max. is 3, abs. min. is 0
(b) abs. max. is 2.828, abs. min. is 0
(c) abs. max. is 3, abs. min. is 2.236

i got "A", is this correct?

2) Find the absolute maximum and absolute minimum values of f(x) =(x) / (x^2+4) on [0, 3]

(a) abs. max. is 0.25, abs. min. is 0
(b) abs. max. is 0.28, abs. min. is 0
(c) abs. max. is 0.25, abs. min. is −0.25

I got "A" is this correct?!?!

1)

f(x) = √(9 − x^2)

f ' (x) = -x /√(9 − x^2)

only critical point is x = 0

evaluate f(x) at critical point x = 0 and at end points -1 and 2

f(0) = √(9) = 3
f(-1) = √(9 − 1) =√8 = 2.828
f(2) = √(9 −4) = √5 = 2.236

absolute max is 3 at critical point x = 0
absolute min is 2.236 at end point x = 2 -------option (c)

2)

f(x) = x /(x^2 + 4)

f ' (x) = [(x^2 + 4) - x (2x) ] /(x^2 + 4)^2

= 4 - x^2 /(x^2 + 4)^2

to get critical point, equate f ' (x) to zero

4 - x^2 = 0

x = -2 and 2

since - 2 is not the given interval [ 0, 3 ]

only critical point in the given interval is x = 2

f(2) = 2 / 8 = 1/4 = 0.25
f(0) = 0
f(3) = 3/13 = 0.231

abs max is 0.25 and abs min is zero -------option (a)

1) c

2) a