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Notes 7-1 Solving Two – Step Equations Example 2x − .4 = 8 +. 4 = + .4 2x = 8.4 2 = 2 First you UNDO addition and subtraction. Second you UNDO multiplication and division. . . This is your solution – – – –> Vocabulary inverse operation solution justify x = 4.2 Description UNDO Do the opposite to both sides of the equal sign (the RIVER) answer - must be in [x = ____ ] form tell which operation/property is used for each step STEPS Another Example 1. Identify your variable. 2y + .2 = 11 2. “What + or – are they doing to your variable?” .. 3. UNDO – Use the inverse operation – .2 = – .2 TO BOTH SIDES of the equal sign. .. 4. “What x or ÷ are they doing to your variable?” 2y = 10.8 5. UNDO – Use the inverse operation TO BOTH SIDES of the equal sign. 6. Solve. 2 = 2 The variable is “y”. They are adding .2 SUBTRACT .2 from both sides of equation. They are multiplying by 2. Divide by 2 on both sides of equation. . y = 5.4 Negative coefficients – x could mean subtract x or add – x, These are the same. – x means the number in front of the variable is –1 . To solve for x , divide both sides by – 1 . (Multiplying both sides by – 1 does the same thing.) Example 12 – 3x = 18 The 12 is NOT subtracted. It is a positive 12. Adding 12 will just make it BIGGER = 24. – 12 – 12 subtract 12 from both sides -3x = 6 -3 -3 then divide both sides by – 3. x = -2