ACT and SAT Math (to help on the ACT and SAT)

quadratic formula - [-b ± √(b² - 4ac)] / (2a) slope formula - (y₂- y₁) / (x₂- x₁) integers - ..., -3, -2, -1, 0, 1, 2, 3, ... rationals - fractions (anything expessable as a ratio of integers) reals - integers, rationals, plus special #s (like √2 or pi) order of opperations - PEMDAS (Parentheses / Exponents / Multiply / Divide / Add / Subtract) Arithmetic Sequences - t₁, t₁+ d, t₁+2d, ... Geometric Sequences - t₁, t₁• r, t₁• r², ... Factors - ex. factors of 52 are 2, 4, 13, and 26 Multiples - ex. multiples of 20 are 40, 60, 80, 100, ... percentages - part = (percent / 100) x whole average - average = sum of terms / number of terms average speed - average speed = total distance / total time sum - sum = average x (number of terms) mode - mode = value in the list that appears most often median - median = middle value in the list fundamental counting principle - if an event can happen in N ways, and another, independent event can happen in M ways, then both events together can happen in N x M ways. probability - probability = number of desired outcomes / number of total outcomes adding exponents - x^a • x^b = x^(a+b) subtracting exponents - x^a / x^b = x^(a-b) negative exponents - 1 / x^b = x^(-b) multiplying exponents - (x^a)^b = x^(a•b) x^0 - 1