Introduction to Substitution

What does it mean to substitute?

• to add different variables together and see what you get

• to graph and find the intersection

• guess and check

• to replace the value of a variable with an equivalent expression

Which one shows the correct substitution for the system?

• 2(2x + 1) - 3y = 7

• 2x - 3(2x + 1) = 7

• y + 2x - 3y = 8

• 2x - 2x + 1 = 7

Which one shows the correct substitution for the system?

x = 7 + y

y = 7 - 2x

• x = 7 + (7 - 2x)

• y = 7 - 7 + y

• x = 7 + 7

• 7 + y = 7 - 2x

Which choice shows substitution correctly?

• 2x + 4(3y - 7) = 9

• 2(3y -7) + 4y = 9

What is the solution to this system? Solve by substitution.
y= 4x + 3
2x - 3y = 21

• (3,-9)

• (-3,-9)

• (-3,9)

• (0,1)

solve by substitution: y=3x+14
y=-4x

• y=3

• y=1

• y= - 2

• y=4

Which equation is correctly using substitution for the system shown?

• x + 6 = -2x − 3

• y = x + 6 − 2x − 3

What should the expression look like when the values (numbers) are substituted in for the variables (letters)?

• 3 + 3 + 2

• 3p + 5q + 2

• 5 + 5 + 2

• 3 + 5 + 2

Using the substitution method to solve this system, what would be the first step?

• Substitute 3x+1 for x in the second equation

• Substitute 3x+1 for y in the second equation

• solve the first equation

Write the new equation to solve after using the substitution process correctly for the system.

y = 5x - 7

-3x - 2y= -12

• -3(5x - 7) - 2y= -12

• -3x - 2(5x-7) = -12

• -3x -2y = 12(5x-7)