Systems of equations by substitution

Presentation

•

Mathematics

•

8th Grade

•

Medium

•

CCSS

8.EE.C.8B, 8.EE.C.7B, 7.EE.B.4A

Standards-aligned

Used 1K+ times

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2 Slides • 17 Questions

Multiple Choice

Given the system

y = 2x + 1

3x + y = -9

What should be substitute into the second equation for y?

WARNING - You need to write this down!

3x + y

-9

2x + 1

Multiple Choice

After substituting the expression in our new equation is____________.

3x + 2x + 1 = -9

2x + 3 = -9

3x + x = -9

None of these.

Multiple Choice

Using the equation in question 3.

What is the value of x?

x = 4

x = -2

x = -3

x = -4

How did we get x?

Multiple Choice

y = -2x + 18
y = 8

(5, 8)

(-5, 8)

(2, 8)

(-2, 8)

Multiple Choice

When solving this system of equations, how will the problem be set up to solve for the first variable?

5x + 4y= −14
y = −7x − 15

5x + 4(-7x - 15) = -14

5(-7x - 15) 4y = -14

-7x - 15 = -14

5x - 7x - 15 = -14

Multiple Choice

What is the next step?

5x + 4(-7x - 15) = -14

add 5 + 4

Distribute 4

subtract -7-15

move the 5 to the other side

Multiple Choice

Solve the system by substitution.

5x + 4y= −14
y = −7x − 15

(-2, -1)

(1, -2)

(-2, 1)

(-1, -2)

Multiple Choice

When solving this system of equation, how will it be set up to solve by substitution?
y = 2x + 1
y = 4x - 1

2(4x - 1) + 1

2x + 1 = 4

2x + 1 = 4x - 1

4(2x + 1) - 1

Multiple Choice

Solve this system of equations.
y = 2x + 1
y = 4x - 1

(1,3)

(-1,-3)

(-1,3)

(3,1)

Multiple Choice

AJ was asked to find the solution to this system of equations.

x = 7 - 2y

2x + y = 5

Noticing that x was isolated and set equal to

7 - 2y, he decided to replace x in the second equation with its value.

What method is AJ using and what equation did he write?

Elimination; 2(7-2y) + y = 5

Graphing; 2x = (7-2y) + y = 5

Substitution; 2(7-2y) + y = 5

Substitution; x = 7 - 2y + 2x + y = 5

Multiple Choice

The solution to a system of equations is any ordered pair that makes both equations true.

TRUE

FALSE

Multiple Choice

What are the steps for graphing a line?

1. Plot y-intercept
2. count slope ratio plot second point
3. Draw the line.

1. Make a table
2. Plot slope
3. Draw line

1. Plot two points
2. Check slope
3. Draw line

1. Draw line
2. Hope it is right

Multiple Choice

What kind of lines have no solution to a system of equations

Parallell Lines

Overlapping lines

Intersecting Lines

Skew Lines

Multiple Choice

^{What is the solution?}

-2

(1, 2)

(1, -1)

Math Response

Rewrite the bottom equation after using substitution. Do not solve the system.

Type answer here

Deg^°

Rad

Match

Read each step of the Substitution method for solving a System of Equations. Then, match the result of performing the step with the step.

Step 1: Solve one equation's variable (expression)

Step 2: Substitute the expression in the other equation

Step 3: Solve the equation for a value

Step 4: Substitute the variable's value in the other equation; solve

Step 5: Present the solution as an ordered pair

y = 5 - 2x

-3x + 6(5-2x) = 0

x = 2

2(2) + y = 5

y = 1

(2, 1)

Dropdown

Colleen was solving the following system of equations by substitution, but she thinks she made a mistake.

Did she? If so, help her fix it!

The mistake was:

2x+5y=19

y=3x-3

Step 1: plug y=3x-3 in for y

2x+5(3x-3)=19

Step 2: Simplify and solve for x

2x+15x-3=19

17x-3=19

17x=22

x=22/17

Step 3: Plug x in and solve for y

y=3(22/17)-3

y=66/17-3

y=66/17-51/17

y=15/17

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