Determine whether g(x)=x2+1x3 is odd, even or neither. Give a reason.
(2 分)
(b)
Determine whether h(x)=cosx is odd, even or neither.
(1 分)
(c)
Find f(2)+f(−2).
(2 分)
題目 2
Use mathematical induction to prove that, for every positive integer n, 1+3+5+⋯+(2n−1)=n2.(5 分)
題目 3
Find the coefficient of x3 in the expansion of (1+2x)5.(5 分)
題目 4
You may use sin2x=2sinxcosx and cosx=sin(2π−x). Solve sin2x=cosx for 0≤x<2π. Give your answers in radians.(5 分)
題目 5
Using e=n→∞lim(1+n1)n, evaluate x→∞lim(1+x3)2x.(5 分)
題目 6
The curve C has equation y=(x2+1)ex.
(a)
Find dxdy.
(3 分)
題目 6 (續)
(b)
Find the gradient of C at x=0.
(2 分)
題目 7
A function G satisfies G′(x)=3x2−4x+2 and G(0)=1.
(a)
Find G(x).
(3 分)
(b)
Hence find G(2).
(2 分)
題目 8
Find the area enclosed by the curve y=x2−1 and the x-axis between x=−1 and x=2.(5 分)
題目 9
Consider the simultaneous equations 2x+y=5 and x−y=1.
(a)
Find the determinant of the coefficient matrix.
(2 分)
(b)
Solve the simultaneous equations.
(3 分)
題目 10
Let a=(1,2,0) and b=(2,−1,2).
(a)
Find a⋅b.
(2 分)
(b)
Find a×b.
(3 分)
B
題目 11
Consider f(x)=xe−x for x≥0.
(a)
Evaluate x→0limxe2x−1.
(3 分)
(b)
Find the stationary point of f and determine its nature.
(5 分)
(c)
Find the equation of the tangent to the graph of y=f(x) at x=2.
(4 分)
題目 12
Consider the curves y=2x and y=x2 for 0≤x≤2.
(a)
Find ∫(2x−x2)dx.
(4 分)
(b)
Find the area enclosed by the two curves.
(5 分)
(c)
Find the value a in 0<a<2 such that the area between the curves from x=0 to x=a is half the enclosed area.
(4 分)
題目 13
For a real parameter λ, consider the system λx+y=1, x+λy=1, whose coefficient matrix is A=(λ11λ).
(a)
Find detA.
(2 分)
(b)
State the values of λ for which the system has a unique solution.
(2 分)
(c)
Solve the system when λ=2.
(4 分)
(d)
Discuss the system when λ=1 and when λ=−1.
(4 分)
題目 14
In three-dimensional space, let A=(0,0,0), B=(4,0,0) and C=(1,3,0). The diagram shows the triangle ABC in the xy-plane.
(a)
Find AB and AC.
(2 分)
(b)
Find the angle BAC, giving your answer to the nearest degree.
(4 分)
(c)
Find AB×AC and hence find the area of triangle ABC.
(4 分)
題目 14 (續)
(d)
Find a unit vector perpendicular to both AB and AC.
(3 分)
參考答案
揀一條題目就會顯示答案同評分指引。建議先自己試做。
第 1 題5 分
1 / (a): g(−x)=x2+1−x3=−g(x), so g is odd. (M1, A1)
1 / (b): cos(−x)=cosx, so h is even. (A1)
1 / (c): The odd terms cancel and the even terms double: f(2)+f(−2)=2cos2. (M1, A1)
第 2 題5 分
2: When n=1, the left-hand side is 1=12, so the statement holds. (B1)
Assume it holds for n=k, so 1+3+⋯+(2k−1)=k2. (M1)
For n=k+1, add the next term 2(k+1)−1=2k+1: the sum is k2+2k+1=(k+1)2. (M1, A1)
Therefore, by mathematical induction, the identity holds for every positive integer n. (C1)
第 3 題5 分
3: By the binomial theorem, the term containing x3 is (35)(1)2(2x)3. (M1)
Its coefficient is (35)×23=10×8=80. (M1, A1)
Answer: 80. (A1, B1)
第 4 題5 分
4: 2sinxcosx=cosx, so cosx(2sinx−1)=0. (M1)
Thus either cosx=0, giving x=2π,23π, or sinx=21, giving x=6π,65π in the stated interval. (M1, A1, A1)
Hence x=6π,2π,65π,23π. (A1)
第 5 題5 分
5: Rewrite the expression as [(1+x3)x/3]6. (M1)
Let n=x/3; as x→∞, n→∞ and the expression in square brackets tends to e. (M1, A1)
Therefore the required limit is e6. (A1, B1)
第 6 題5 分
6 / (a): By the product rule, dxdy=2xex+(x2+1)ex=ex(x2+2x+1)=ex(x+1)2. (M1, A1, A1)
6 / (b): At x=0, dxdy=1. The gradient is 1. (M1, A1)
第 7 題5 分
7 / (a): Integrating, G(x)=x3−2x2+2x+C. (M1, A1)
Using G(0)=1 gives C=1, so G(x)=x3−2x2+2x+1. (M1, A1)
7 / (b): G(2)=8−8+4+1=5. (A1)
第 8 題5 分
8: The curve crosses the x-axis at x=−1 and x=1. It is below the axis on [−1,1] and above it on [1,2]. (M1, A1)
Area =∫−11(1−x2)dx+∫12(x2−1)dx. (M1)
The first integral is 34 and the second is 34. (M1)
Total area =38 square units. (A1)
第 9 題5 分
9 / (a): The coefficient matrix is (211−1). Its determinant is 2(−1)−1(1)=−3. (M1, A1)
9 / (b): Adding the equations gives 3x=6, hence x=2. (M1, A1)
Substitution into x−y=1 gives y=1. The solution is (x,y)=(2,1). (M1)
11 / (a): Put u=2x. Then xe2x−1=2ueu−1. (M1)
Using u→0limueu−1=1, the limit is 2. (M1, A1)
11 / (b): f′(x)=e−x(1−x). (M1, A1)
The stationary point satisfies 1−x=0, so x=1 and f(1)=1/e. (M1, A1)
For 0≤x<1, f′(x)>0, and for x>1, f′(x)<0, so this is a maximum. (M1)
11 / (c): At x=2, f(2)=2e−2 and f′(2)=−e−2. (M1, A1)
The tangent is y−2e−2=−e−2(x−2), or y=(4−x)e−2. (M1, A1)
第 12 題13 分
12 / (a): ∫(2x−x2)dx=x2−3x3+C. (M1, A1, A1, A1)
12 / (b): The curves intersect where 2x=x2, so x=0,2. On this interval 2x≥x2. (M1, A1)
Area =∫02(2x−x2)dx=[x2−3x3]02=34 square units. (M1, A1, A1)
12 / (c): Half the enclosed area is 2/3. Hence a2−3a3=32. (M1, A1)
Rearranging gives a3−3a2+2=0=(a−1)(a2−2a−2). The roots are 1,1±3; only a=1 lies in (0,2). (M1, A1)
第 13 題12 分
13 / (a): detA=λ2−1=(λ−1)(λ+1). (M1, A1)
13 / (b): A unique solution exists when detA=0, hence when λ=1,−1. (M1, A1)
13 / (c): For λ=2, the equations are 2x+y=1 and x+2y=1. Subtracting gives x−y=0, so x=y. (M1, A1)
Then 3x=1, so x=y=31. (M1, A1)
13 / (d): If λ=1, both equations reduce to x+y=1, so there are infinitely many solutions. (M1, A1)
If λ=−1, the equations are −x+y=1 and x−y=1. The first implies x−y=−1, contradicting the second; there is no solution. (M1, A1)
第 14 題13 分
14 / (a): AB=B−A=(4,0,0) and AC=C−A=(1,3,0). (M1, A1)
14 / (b): AB⋅AC=4 and ∣AB∣=4, ∣AC∣=10. (M1, A1)
Thus cos∠BAC=4104=101, so ∠BAC≈72∘. (M1, A1)
14 / (c): AB×AC=(0,0,12). (M1, A1, A1)
The area of triangle ABC is half the magnitude of this vector: 21(12)=6 square units. (A1)
14 / (d): A normal vector is (0,0,12), whose magnitude is 12. (M1, A1)
A unit vector perpendicular to both is (0,0,1); its negative is also acceptable. (A1)