Tham khảo tài liệu 'math test english 3', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | ----------------------------- ACT MATH TEST PRACTICE ------------------------------------ When 14 is added to a number x the sum is less than 21. x 14 21 The sum of a number x and four is at least nine. x 4 9 When seven is subtracted from a number x the difference is at most four. x - 7 4 Assigning Variables in Word Problems It may be necessary to create and assign variables in a word problem. To do this first identify an unknown and a known. You may not actually know the exact value of the known but you will know at least something about its value. Examples Max is three years older than Ricky. Unknown Ricky s age x Known Max s age is three years older Therefore Ricky s age x and Max s age x 3 Siobhan made twice as many cookies as Rebecca. Unknown number of cookies Rebecca made x Known number of cookies Siobhan made 2x Cordelia has five more than three times the number of books that Becky has. Unknown the number of books Becky has x Known the number of books Cordelia has 3x 5 Substitution When asked to substitute a value for a variable replace the variable with the value. Example Find the value of x2 4x - 1 for x 3. Replace each x in the expression with the number 3. Then simplify. 3 2 4 3 - 1 9 12 - 1 20 The answer is 20. 154 ------------------------------ ACT MATH TEST PRACTICE ------------------------------------- Intermediate Algebra Intermediate algebra covers many topics typically covered in an Algebra II course such as the quadratic formula inequalities absolute value equations systems of equations matrices functions quadratic inequalities radical and rational expressions complex numbers and sequences. The Quadratic Formula x b ijac for quadratic equations in the form ax2 bx c 0. The quadratic formula can be used to solve any quadratic equation. It is most useful for equations that cannot be solved by factoring. Absolute Value Equations Recall that both 5 5 and -5 5. This concept must be used when solving equations where the variable is in the absolute value
