KEY Section 4: Applied Mathematics
Section 1: Algebra
4.1 2
1.1 9 λ = (2n + 1)2 π4 ,
1.2 b,c u = C sin(2n + 1) π2 , n = 0, 1, 2, · · ·
1.3 The multiplicative group {−1, 1}
1.4 a,c 4.2
−2
1.5 a − 2b − c = 0 c=
b−a
1.6
1 3 4
1 0 2 4.3
π
0 1
0 √
2
1
7
0 0 3
4.4
1.7 0 x2 − x
y(x) =
1.8 a,b,c 4
1.9 a √
1.10 λ2 − 3 2λ + 4 4.5 L(y 00 )(s) = s2 L(y)(s) − sy(0) − y 0 (0)
4.6 x = 0, irregular singular point, x = 1, regular
Section 2: Analysis singular point
2.1 sin 1 4.7 0
2.2 4 4.8 y(x) = x3 + C1 x2 + C2
e
2.3 b,c 4.9
2.4 a,b Z b
(b − a)
2.5 R\{−1} f (x) dx ∼ [f (a) + 4f ((a + b)/2)) + f (b)]
a 6
2.6 b
2.7 4.10 3
Z 1
0
|f (t)| dt Section 5: Miscellaneous
0
5.1
2.8 m!(m + 1)!
∞ 2n
X
n−1 x
(−1) (m − n + 1)!
n=1
(2n − 1)(2n)
5.2 2n−1 (3n + 2)
(4n+1)π
2.9 e , n∈Z 5.3 a,b
2.10 {z = x + iy : y ≥ 0} 5.4 log N
5.5 0
Section 3: Topology 3 2
5.6 √ − 16x + 64x − 9 = 0
x
3.1 b 5.7 37
3.2 a,c 5.8
a + 3b
3.3 B and D are homeomorphic
3.4 a,b,c 4
3.5 a,b
3.6 a,b 5.9 a,b
3.7 b 5.10 a,b
3.8 a,b
3.9 c
3.10 b,c