
P1: JXR
MHDQ256-APP-B MHDQ256-Smith-v1.cls January 12, 2011 7:22
LT (Late Transcendental)
CONFIRMING PAGES
APPENDIX B
..
Answers to Odd-Numbered Exercises A-63
33. (a) 16, 4, 24, −16, −4, −24,
√
848, −
√
848
(b)
0, 16, 0
,
0, −16, 0
, 16, −16
35. (a) 1.5 (b) −1 37. parallel
39.
2a, −a
, a = 0
−3
5.0
−2
x
2.5
−1
−1.0
−0.5
0.00
0.0
1
0.5
y
−2.5
1.0
2
−5.0
3
−3
−3
−2
y
−2
x
−1.0
−1
−1
−0.5
0.0
0
0
0.5
1
1.0
1
2
2
3
3
41. 2(x − 1) +3(y +1) −z = 0,
The equation of the normal line is
⎧
⎨
⎩
x = 1 + 2t
y =−1 +3t
z =−t
43. −2(x + 1) +4(y −2) +2(z −1) = 0,
The equation of the normal line is
⎧
⎨
⎩
x =−1 −2t
y = 2 + 4t
z = 1 + 2t
45. (0, 0, 0), (1, 1, −1), (−1, −1, −1)
47. a = 2, b = 1
49.
y
x
51. 2, −2 53. (a) true (b) true 55. 0
57. −tan10
◦
, tan 6
◦
≈−0.176, 0.105, 11.6
◦
59. (a) 8, 4 (b) Ellipse 61. 0.8, 0.3, −0.004
63. If the shark moves toward higher charge, it moves in the direction
12, −20, 5.
Exercises 13.7, page 884
1. (0, 0) saddle 3. (0, 0) saddle, (1, 1) local min
5. (0, 1) local min, (±2, −1) saddle 7. (0, 0) max
9.
(
1, 1
)
local min 11.
1
√
2
, 0
local max,
−
1
√
2
, 0
local min
13. (0, 0) saddle, (1, 1) and (−1, −1) local min
15. (0, 0) saddle, ±
1
2
,
1
2
local max, ±
1
2
, −
1
2
local min
17. (2.82, 0.18) local min, (−2.84, −0.18) saddle, (0.51, 0.99) saddle
19. (±1, 0) local max,
0, −
3
2
local max,
0,
3
2
local min, (0, 0) saddle,
±
√
19
3
√
3
, −
2
3
saddle
23. (a) 247, 104 (b) 276, 95
25. (−0.3210, −0.5185), (−0.1835, −0.4269)
27. (0.9044, 0.8087), (3.2924, −0.3853)
29. (0, 0) is a saddle point 31. f (2, 0) = 4, f (2, 2) =−2
33. f (3, 0) = 9, f (0, 0) = 0
35. max : e
−1
at (1, 1);
min:0at(0, y) and (x, 0)
37. a = b = c =
2
3
s
39. (a) f (x, 0) = f (0, y) = 0; minima
(b) f (x, 0) = f (0, y) = 0; minima
43. (a) Local max for k = 0, inflection at x = 0 for k = 0
(b) All traces have a local min at origin
45. false 47. false
49. extrema at
±
π
2
, ±
π
2
, saddles at (±nπ, ±mπ)
51. (1, 0), f (1, 0) < f (−10, 0)
53. (a) d(x, y) =
(x − 3)
2
+ (y +2)
2
+ (3 − x
2
− y
2
)
2
,
(1.55, −1.03, 0.54)
(b)
1, −
3
2
,
√
13
2
55. (a) 4ftby4ftby4ft (b)
4
3
√
6ftby
4
3
√
6ftby2
√
6ft
57. x = y ≈ 1.42 m; 24.55 > 17.85
Exercises 13.8, page 894
1. x =
6
5
, y =−
2
5
3. x = 2, y =−1
5. x = 1, y = 1 7. x = 1, y = 1
9. max : f (2, 2) = f (−2, −2) = 16,
min : f (2, −2) = f (−2, 2) =−16
11. max : f
4
3
,
4
3
=
256
27
,
min : f
(
x, 0
)
= f (0, y) = 0
13. max : f
(17 −1)/8, (
√
17 −1)/2
=
√
17 −1
8
e
(
√
17−1)/2
,
min : f
−
(17 −1)/8, (
√
17 −1)/2
=−
√
17 −1
8
e
(
√
17−1)/2
15. max : f (±
√
2, 1) = 2e, min = f (0, ±
√
3) = 0
17. max : f
±
2
(
18
)
1/4
, ±
1
(
18
)
1/4
, ±
1
(
18
)
1/4
=
√
18,
min : f
(
0, 0, ±1
)
= f
(
0, ±1, 0
)
= f
(
±1, 0, 0
)
= 1
19. no max or min
21. max : f
a
2
√
1 +a
2
,
1
√
1 +a
2
=
√
1 +a
2
,
min : f
−
a
2
√
1 +a
2
, −
1
√
1 +a
2
=−
1 +a
2
23. If a and b both are even then for all points
f
±
a
a + b
, ±
b
a + b
=
a
a + b
a
b
a + b
b
, maxima
f (0, ±1) = f (±1, 0) = 0, minima
If a and b both are odd then
f
±
a
a + b
, ±
b
a + b
=
a
a + b
a
b
a + b
b
,
maxima
f
±
a
a + b
, ∓
b
a + b
=−
a
a + b
a
b
a + b
b
,
minima