tailieunhanh - Sat - MC Grawhill part 32

Tham khảo tài liệu 'sat - mc grawhill part 32', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 300 MCGRAW-HILL S SAT Lesson I Solving Equations Equations as Balanced Scales Algebra is really common sense once you start thinking of every equation as a balanced scale. The terms on either side of the equals sign must be balanced just like the weights on a scale. The laws of equations come from the commonsense rules for keeping a scale balanced. Imagine that you are the keeper of a scale and you must keep it balanced. What would you do if someone took weights from one side of the scale You d remove an equal weight from the other side of course. This is a law of equality anything you do to one side of the equation you must do to the other to maintain the balance. Example If 12x - 8 28 then what is the value of 3x - 2 Don t worry about solving for x because that s not what the question is asking for. Notice that the expression you are given 12x - 8 is 4 times the expression you are looking for 3x - 2. So to turn the given expression into the one you want divide by 4. Of course you must do the same to the other side to keep the balance 12x - 8 28 . 3x - 2 7 44 Solving as Unwrapping Solving simple algebraic equations is basically the same thing as unwrapping a present. And it s just as fun too right Okay maybe not. Wrapping a present involves a sequence of steps 1. Put the gift in the box. 2. Close the box. 3. Wrap the paper around the box. 4. Put the bow on. Here s the important part unwrapping the present just means inverting those steps and reversing their order 1. Take off the bow. 2. Unwrap the paper. 3. Open the box. 4. Take out the gift. Example Solve for x 5x2 - 9 31 The problem is that x is not alone on the left side it is wrapped up like a gift. How is it wrapped Think of the order of operations for turning x into 5x2 - 9 1. Square it x2 2. Multiply by 5 5x2 3. Subtract 9 5x2 - 9 So to unwrap it you reverse and invert the steps 1. Add 9 5x2 - 9 9 5x2 2. Divide by 5 5x2 5 x2 3. Find the square roots both of them 4x x I If you perform these steps to both .