, 
2
4
(
3)
x
x
−
+ Let
f (x) = (x – 3)2 + x4
or
f ′(x) = 2(x – 3) + 4x3 = 2(x – 1) (2x2 + 2x + 3)
Thus, f ′(x) = 0 gives x = 1 or 2x2 + 2x + 3 = 0 for which there are  no real roots Also, there are no end points of the interval to be added to the set for which f ′ is zero,
i e