M2T3 - Review - Part I

M2T3 - Review

Part I

Systems of Linear Equations

Systems of Linear Equations

• Solution = Intersection

• One solution, no solution, and infinite many solutions

• Solving methods: graphing, substitution, and linear combination

Solutions

The solution to a system of linear equations is the intersection between the lines of those equations. This is when all of the equations simultaneously share an input and an output.

Solutions

Systems of linear equations can have the following numbers of solutions:

- One solution - lines with different slopes will intersect once across their domains

- No solution - Parallel lines (same slope, different y-intercept) will never intersect, and therefore, have no solution

- Infinite many solutions - Equations of the same lines will intersect at ALL TIMES across their entire domain, and therefore, have infinite many soltuions

Methods of Solving

- Graphing - We can graph the lines of systems of equations to find their intersection point

Multiple Choice

Solve:
-2x + 5y = -1
4x - 2y = -6

• (-2, -1)
• (2, 7)
• (3, 1)
• (-1, -2)

Multiple Choice

Solve the system of equations.
y = 4x+1
3x + 2y = 13

• (1, 5)
• (5, 1)
• (0.25, 2)
• ∅

Methods of Solving

- Substitution - We can isolate a variable to substitute an express into another equation to solve for the remaining variable

Multiple Choice

Solve the system of equations.
y = 4x+1
3x + 2y = 13

• (1, 5)
• (5, 1)
• (0.25, 2)
• ∅

Multiple Choice

Solve the following system using any method.

y = 2x + 1

y = 4x - 1

• (1,3)

• (-1,-3)

• (-1,3)

• (3,1)

Multiple Choice

Solve the following system using any method.

y = 2/3x - 2

y = -x + 3

• (0,3)

• (0,-3)

• (3,0)

• (-3,0)

Methods of Solving

- Linear Combination/Elimination - We can re-write equations to produce additive inverses of a variable to eliminate a variable, which allows us to solve for the remaining variable

Multiple Choice

Solve the following system using any method.

y = 2x + 1

y = 4x - 1

• (1,3)

• (-1,-3)

• (-1,3)

• (3,1)

Multiple Choice

Solve the following system using any method.

3x + 2y = 16

7x + y = 19

• (-2,5)

• (-2,-5)

• (2,-5)

• (2,5)

Methods of Solving

- Once we have identified the solution to one of our variables, we can substitute that solution into one of our equations to solve for the remaining variable

Multiple Choice

A large pizza at Palanzio’s Pizzeria costs $6.80 plus $0.90 for each topping. The cost of a large cheese pizza at Guido’s Pizza is $7.30 plus $0.65 for each topping. Which system of equations could be used to find the number of toppings when both companies cost the same amount? 

• y = 6.80 + .65x
  y=7.30+.90x
• x + y = 6.80
  x + y = 7.30
• y = 6.80+.90x
  y = 7.30 + .65x
• y + .90x = 6.80
  y + .65x = 7.30

Multiple Choice

Your family goes to a restaurant for dinner. There are 6 people in your family. Some order the chicken dinner for $14.80, and some order steak for $17. If the total bill was $91, which system best represents the situation? 

• x + y = 6
  14.80x + 17y = 91
• x + y = 91
  14.80x + 17y = 6
• x + y = 6
  14.80y + 17x = 91
• x + y = 91
  14.80x+ 17y = 6

Multiple Choice

Last season two running backs on the Steelers football team rushed a combined total of 1550 yards.  One rushed 4 times as many yards as the other.  Let x and y represent the number of yards each individual player rushed. Which system of equations could be used? 

• x + y = 1550
  y  = 4x
• x + y = 1550
  y = x + 4
• y - x = 1550
  y = 4x
• y = 1550 + x
  y = x + 4

Multiple Choice

Nancy went to the grocery story.  On Monday she purchased 4 apples and 6 bananas for a total of $13.  On Wednesday she purchased 3 apples and 7 bananas for a total of $13.50.  Which system of equations represents the situation?

• 4x + 6y = 3
  13.5x - 13y = 6
• x + y = 4
  x - y = 6
• 4x + 6y = 13
  3x + 7y = 13.5
• 4x - 6y = 13
  3x - 7y = 13.5

Questions?