Sequences & Series A set of numbers where each successive term differs from the preceding term by the same constant. Eg. 20, 18, 16, 14, 12, 10, … [ Differs by the constant -2 ] Terms used: a n n th term l last term a first term d common difference r common ratio
Arithmetic Progression A progression in which there is a common difference between each term and the consecutive term. a n = a + (n - 1) d S n = n (a + l ) 2 = n (2a + (n - 1)d) 2
Geometric Progression A progression in which there is a common ratio between each term and the consecutive term. a n = ar (n - 1) S n = a(1 - r n ) when |r| < 1 1 - r S n = a(r n - 1) when |r| > 1 r - 1
Sum to Infinity For GPs with |r|<1 there exists a sum to infinity since such series tend to zero, i.e. they are convergent series. S n = a 1 - r
Sigma ( Σ ) Notation b Σ (a n ) = S n n = a = a + a a+1 + a a+2 +... a b
DIFFERENTIATION
First and Second Derivatives For a function y = ax n + bx m First derivative, f’(x) or y’ or dy = anx (n - 1) + bmx (m - 1) dx Second Derivative, f”(x) or y” or d 2 y = d( dy / dx ) dx 2 dx
Chain, Product and Quotient Rules CHAIN RULE For y in terms of x, where x can be written in terms of t dy = dy × dt dx dt dx Shortcut method: f’(x) = (g(h(x)))’ = g’(h(x))h’(x) PRODUCT RULE For y = uv where u and v are in terms of x y’ = uv’ + vu’ QUOTIENT RULE For y = u / v where u and v are in terms of x y’ = vu’ - uv’ v 2
Stationary Points A stationary point is where the first derivative, y’ = 0. The nature of a stationary point can be determined by the second derivative test: if y” < 0 then it is a maximum if y” > 0 then it is a minimum
Rates of Change RATE - a measure of change of a quantity in relation to another quantity CHANGE - an increase or decrease in value of a quantity Rates of Change can often be expressed as the derivative of a quantity with respect to another, i.e. dy/dx