Steps Systems of Equations by Substitution

What is the first step in solving a system by Substitution?

• Make sure both equations are in standard form.

• Make sure at least one equation is solved for one variable.

• Make sure both equations are in slope-intercept form.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Why does substitution help us solve a system of equations?

• It changes one variable to an expression using the other variable, so we can solve an equation that only has one variable at a time.

• It creates a problem with fewer steps.

• It puts both equations in slope-intercept form for easy graphing.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

TRUE or FALSE:

When both equations have the same variable isolated

(both y = or both x = ),

substituting the first into the second ends up looking like

you just set the two equal to each other.

• TRUE

• FALSE

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Which option shows the CORRECT substitution for this system?

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Find the value of (x, y) that satisfies the equations by solving the system using substitution.
 
5x + 4y= −14
y =  −7x  −  15  The solution is (a)   .

• (-2, -1)

• (0, 0)

• (1, 1)

• (2, 2)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve the system of linear equations by substitution.

-5x + 3y = 51

y = 10x - 8​

​ ​ ​ (a)   ​ (b)  

• y = -22

• x = -3

• x = 59/25

• y = 15.6

• x = 3

• y = 22

• x = -8

• y = 4

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve the system of linear equations by substitution.

• x = 6

• x = -3

• y = 2

• y = 5/9

• x = 1

• y = 1

• x = -8

• y = 4

• x = -2

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve by Substitution:

x = -3y - 17

2x + 3y = -7

• (1, -20)

• (3, 0)

• (-5, -2)

• (10 , -9)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve the system of linear equations by substitution.

• y = -22

• x = -3

• x = 1

• y = -4

• x = 5

• y = -8

• x = -8

• y = 4

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the first step when solving the system using the substitution method?

y=2x+4

2x+3y=20

Substitute ​ (a)   ​ for ​ (b)   in the 2nd equation to get ​ (c)  

• 2x+4

• y

• 2x+3(2x+4)=20

Answer explanation

y=2x+4

2x+3y=20

Substitute 2x+4 for y in 2x+3y=20 to get:

2x+3(2x+4)=20

then you can solve that equation for x

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6