Simultaneous Equations by Substitution

Solve the system of equations using substitution:

-4x + 4y = 8

y = -2x - 10

• (-4, -2)

• (12, -34)

• (4, -18)

• (-2, -6)

Solve the simultaneous equations by substitution

x+y=5

x-y=1

• x=2, y=3

• x=3, y=2

• x=3, y=-2

• x=-3, y=2

Solve the system by substitution:

y = x + 5
4x + y = 20

• (3,8)
• (8,3)
• (0,2)
• (2,0)

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.
• Make sure both equations can be solved.

Christian had brochures printed for a new business venture. Christian originally ordered 4 boxes of black-and-white brochures and 3 boxes of colour brochures, which cost a total of $134. After those ran out, Christian spent $120 on 3 boxes of black-and-white brochures and 3 boxes of colour brochures. Which system represents this situation?

• x+y=134
  x+y=120
• 3x+3y=134
  4x+3y=120
• 4x+3y=134
  3x+3y=120
• 7xy=134
  6xy=120

• (1, 2)

• (1, 1)

• (2, 1)

• (2, 2)

Solve the simultaneous equations

a+b=11

a-b=3

• a=7, b = 4

• a=-4, b= 7

• a=4, b = 7

• a=4, b= -7

3x + y = –14

–2x – y = 9

Which method would be best for solving this system?

• Substitution

• Elimination/Matrices