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HW, red pen, book, HW, red pen, book, pencil on desk.pencil on desk.

Solving 2-step Solving 2-step equationsequations

Lesson 7-1 p.336Lesson 7-1 p.336

2-step equations2-step equations

In chapter 2 we learned how to solve In chapter 2 we learned how to solve simple equations.simple equations.

For example to solve 5 + n = -8 we For example to solve 5 + n = -8 we learned to subtract 5 from both sides of learned to subtract 5 from both sides of the equation like this:the equation like this:

5 + n = -85 + n = -8 -5 -5-5 -5 subtract 5subtract 5 n = -13n = -13 solutionsolution

2-step equations2-step equations

We also solved equations like this:We also solved equations like this:

-4n = 12-4n = 12

-4n-4n = = 1212 divide both sides by -4divide both sides by -4 -4-4 -4 -4 n = -3n = -3 solutionsolution

Solving 2-step equationsSolving 2-step equations

Now we are going to combine 2 operations in Now we are going to combine 2 operations in one equation.one equation.

For example, let’s try 3n – 6 = 15For example, let’s try 3n – 6 = 15

3n – 6 = 153n – 6 = 15 +6 +6+6 +6 first add 6 to both sidesfirst add 6 to both sides 3n3n = = 2121 then divide by 3then divide by 3 3 33 3

n = 7n = 7 solutionsolution

Solving 2-step equationsSolving 2-step equations

It is a good practice to check our answer.It is a good practice to check our answer. Our original equation was 3n – 6 = 15Our original equation was 3n – 6 = 15

Our solution was n = 7Our solution was n = 7 If we substitute 7 for the n we getIf we substitute 7 for the n we get 3(7) – 6 = 153(7) – 6 = 15 21 - 6 = 1521 - 6 = 15 15 = 1515 = 15

Another exampleAnother example

TT - 10 = -6 - 10 = -6 44

TT - 10 = -6 - 10 = -6 4 4 +10 +10+10 +10 add 10 to both sidesadd 10 to both sides

(4)(4)TT = 4 (4) = 4 (4) multiply both sides by 4multiply both sides by 4 44

T = 16T = 16 solutionsolution

Try ThisTry This

15x + 3 = 4815x + 3 = 48

9g + 11 = 29g + 11 = 2

-9 - -9 - yy = -12 = -12

77

Try ThisTry This

15x + 3 = 4815x + 3 = 48 x = 3x = 3

9g + 11 = 29g + 11 = 2

-9 - -9 - yy = -12 = -12

77

Try ThisTry This

15x + 3 = 4815x + 3 = 48 x = 3x = 3

9g + 11 = 29g + 11 = 2 g = -1g = -1

-9 - -9 - yy = -12 = -12

77

Try ThisTry This

15x + 3 = 4815x + 3 = 48 x = 3x = 3

9g + 11 = 29g + 11 = 2 g = -1g = -1

-9 - -9 - yy = -12 = -12 y = 21y = 21

77

Watch your signsWatch your signs

In a problem like 5 – x = 17, remember In a problem like 5 – x = 17, remember that the coefficient of x is -1.that the coefficient of x is -1.

To solve first subtract 5 like this:To solve first subtract 5 like this: 5 – x = 175 – x = 17 -5 -5-5 -5 (-1)(-1) -x = 12 -x = 12 (-1)(-1) Then multiply both Then multiply both

sidessides by -1 by -1 x = -12x = -12

Try ThisTry This

-a + 6 = 8-a + 6 = 8

Try ThisTry This

-a + 6 = 8-a + 6 = 8 a = -2a = -2

Agenda 1-18-11Agenda 1-18-11

P.A. #1P.A. #1

P.338P.338

#11-25#11-25