How Not to Graph f (x) = sin 63x: sin 63x
sin 63x
Applications of the Mean Value Theorem:
If f 0(x) = 0 for all x in an interval, then f is constant there.
If f 0(x) > 0 for all x in an interval, then f is increasing there.
If f 0(x) < 0 for all x in an interval, then f is decreasing there.
More Applications of the Mean Value Theorem: If f 00(x) > 0 for all x in an interval, then f 0 increases there.
The curve “cups up”, or is “concave upward”.
If f 00(x) < 0 for all x in an interval, then f 0 decreases there.
The curve “cups down”, or is “concave downward”.
Wherever f 00(x) changes sign, we have a Point of Inflection.
f 00(x) < 0
f 00(x) < 0 f 00(x) > 0
f 00(x) > 0
At an inflection point, f 00(x) usually equals 0 or doesn’t exist.
f <0
f (x) = x3 − x4
= x (1 − x) Roots at 0 and 1 2
f (x) = 3x − 4x
3
f0 > 0
1
f0 > 0 0
2
f (x) = 6x − 12x
2
f 00 < 0 f 00 > 0 ∩ ∪ 0
= 6x(1 − 2x) 1 ) Inflection points at (0, 0) and at ( 12 , 16
Important x’s: 0, 12 , 34 , 1.
f0 < 0 3 4
= x (3 − 4x) 27 ) Leveling at (0, 0), Maximum at ( 34 , 256 00
f <0
0
3
0
f >0
1 2
f 00 < 0 ∩
1 27 Important y’s: 0, 16 , 256 .
Initial Steps:
27 ( 34 , 256 )
1 ) ( 12 , 16
0 Completed Graph:
1 27 ( 34 , 256 )
1 ) ( 12 , 16
x
0
1
x
What might happen with a misdrawn inflection point:
1 ) ( 12 , 16
27 ( 34 , 256 )
0
1
x
1
√ f <0 f (x) = x − x 0 4 Equals 0 only at 0 0 0 1 1 f < 0 f >0 0 f (x) = − √ 0 4 4 2 x √ x−2 = √ 4 x Endpoint Maximum and Absolute Maximum at (0, 0)
9
9
Absolute Minimum at (4, −1), Endpoint Maximum at (9, − 34 ) 00
1
− 32
f (x) = − x > 0, 4 Important x’s: 0, 4, 9.
so graph is always concave upward. Important y’s: 0, − 34 , −1.
0 1 2 3 4 5 6 7 8 9 Initial Steps:
(4, −1)
(9, − 34 )
0 1 2 3 4 5 6 7 8 9
Completed Graph:
(4, −1)
(9, − 34 )