1. 1.3 Solving Systems by Substitution

2. Steps for Substitution 1.Solve for the “easiest” variable 2.Substitute this expression into the other equation 3.Solve for remaining variable 4.Substitute the value into the starting equation to solve for final variable 5.Write as ordered pair and check

3. Solve by Substitution 3X + Y = 8 18X + 2Y = 4

4. Show me how to solve by Substitution !! X = Y + 3 2X + 2Y = 2

5. Steps for Elimination 1.Line up the equations. 2.Look to see if you add the “columns” if either variable is eliminated. 3.If it isn’t, look to see what you could multiply by to eliminate a variable. 4.Rewrite the equation you need to multiply and multiply the whole equation by that number. 5.Rewrite the other equation under it. 6.Add the “columns.” 7.Solve for that variable. 8.Substitute that answer into one of the original equations and solve for the other variable. 9.Write it as an ordered pair.

6. Solve by Elimination 2X + Y = 8 X – Y = 10 X – Y = 10

7. Solve by Elimination 3X + Y = 8 18X + 2Y = 4

8. Solve by Elimination X + Y = 4 2X + 3Y = 9

9. 2X – 4Y = 5 –X + 2Y = 8 Solve by Elimination

10. 4Y + 30 = 10X 5X – 2Y = 15

11. – 4.5x + 7.5Y = – 9 3x – 5Y = 6 3x – 5Y = 6 Multiply by ten to eliminate decimals. – 45X+ 75 Y= – 90 3X – 5Y = 6 3X – 5Y = 6 Y u c k ! !

13. 2x – 3y + 4z = 8 3x + 2y = 7 x = 1 What size is the system?

14. Let’s look at Page 15 # 22 Take the words and build a system of equations.

15. Assignment