Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Section 2.1 The Addition Principle of Equality
2 Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Equations An equation uses an equal sign (=) and indicates that two expressions are equal = 13 An equation always has an equal sign = x The solution of an equation is the number which makes the equation true = is the solution for this equation since it makes = x true.
3 Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Equivalent Equations Equations that have exactly the same solution are called equivalent equations. x = 7 7 is the solution to the equation 6 + x = x = 13 The process of finding all solutions of an equation is called solving the equation.
4 Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. The Addition Principle 6 + x = 13 Left sideRight side We need to find the value of x. 6 + x + ( 6) = 13 + ( 6) Adding ( 6) to both sides of the equation will maintain the balance of the equation. x = 7 Solution to the equation. The Addition Principal If the same number is added to both sides of an equation, the results on both sides are equal in value.
5 Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Example a 6.2 = 3.5 Check your answer in the original equation. a (6.2) = (6.2) 6.2 is the opposite of 6.2. Add 6.2 to both sides of the equation. a = 2.7 (2.7) 6.2 = 3.5 Solve a 6.2 = 3.5.
6 Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Example Solve for c. 3c 8 = 2c 15 3c = 2c Add 8 to both sides of the equation. 3( 7) 8 = 2( 7) 15 3c = 2c 7 3c + ( 2c) = 2c 7 + ( 2c) Add 2c to both sides of the equation. c = 7 21 8 = 14 15 29 = 29 Check your answer in the original equation.
7 Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Example Is 5 the solution of the equation – = x – 2? Solve for the solution. Thus, 5 is not the solution. Substitute 5 for x and see if we obtain an identity. – = x – 2 – = 5 – 2 –6 ≠ 3 – = x – 2 –6 = x – 2 –4 = x Check: Replacing x with –4 in the original equation, verifies the solution.
8 Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Example Find the value of y that satisfies the equation The LCD is 10. Be sure to check your answer in the original equation. Add to both sides of the equation and simplify. Simplify.