Concept Review
Click each topic to expand key formulas, memory aids, and worked examples
Arithmetic Sequence
- \(d\) = common difference = \(u_2 - u_1\)
- \(u_n\) is the nth term; \(u_1\) is the first term
- \(S_n = \frac{n}{2}(u_1 + u_n)\) — sum using first and last
Geometric Sequence
AP: \(u_1 = 3,\ d = 5\). Find \(u_{10}\).
\(u_{10} = 3 + 9(5) = 3 + 45 = \mathbf{48}\)
GP: \(u_1=2,\ r=3\). Find \(S_5 = \frac{2(3^5-1)}{3-1} = \frac{2 \times 242}{2} = \mathbf{242}\)
Laws of Exponents
Logarithm Rules
Quadratic Formula & Discriminant
- \(\Delta > 0\): two distinct real roots
- \(\Delta = 0\): one repeated root
- \(\Delta < 0\): no real roots
- Completing the square: \(x^2+bx = (x+\tfrac{b}{2})^2 - \tfrac{b^2}{4}\)
Binomial Theorem
Coefficient of \(x^2\) in \((1+x)^5\):
\(\binom{5}{2} = \frac{5!}{2!\cdot3!} = \mathbf{10}\)
Key Definitions
Domain: all valid inputs (x-values). Range: all possible outputs (y-values).
Inverse Function
Composite Function
- The graph of \(f^{-1}\) is the reflection of \(f\) in \(y=x\)
- \(f(f^{-1}(x)) = f^{-1}(f(x)) = x\)
- Exponential growth: \(y = ka^x\) where \(a>1\)
- Exponential decay: \(y = ka^x\) where \(0<a<1\)
\(f(x) = 3x - 2\). Find \(f^{-1}(x)\).
Let \(y = 3x-2 \Rightarrow x = \frac{y+2}{3} \Rightarrow f^{-1}(x) = \frac{x+2}{3}\)
\(f^{-1}(7) = \frac{7+2}{3} = 3\)
Differentiation Rules
Chain, Product & Quotient Rules
Integration
- Tangent slope at \(x=a\) is \(f'(a)\)
- Max/min: set \(f'(x)=0\) and check \(f''(x)\)
- \(f''(a)>0\): local min; \(f''(a)<0\): local max
- Definite integral = signed area under curve
\(f(x) = 3x^2 + 2x\). Find \(f'(x)\) and \(f'(2)\).
\(f'(x) = 6x + 2\) → \(f'(2) = 6(2)+2 = \mathbf{14}\)
\(\int_0^3(2x+1)\,dx = [x^2+x]_0^3 = (9+3)-0 = \mathbf{12}\)
Key Trig Values (Radians)
Probability
Statistics
Vectors
- Normal dist: ~68% within 1σ, ~95% within 2σ
- If \(\mathbf{a}\cdot\mathbf{b}=0\), vectors are perpendicular
- Area of circle: \(\pi r^2\); Circumference: \(2\pi r\)
- Exponential model: \(P = P_0 e^{kt}\)
P(A)=0.4, P(B)=0.3, P(A∩B)=0.1 → P(A∪B) = 0.4+0.3−0.1 = 0.6
Mean of {2,4,6,8,10} = 30/5 = 6
z-score: X=75, μ=70, σ=5 → z = (75−70)/5 = 1.0
Exam Questions
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✦ Complete Solutions & Explanations
Step-by-step workings for all 20 questions