Solving Systems of Equations The Elimination Method
Objectives Learn the procedure of the Elimination Method using addition Learn the procedure of the Elimination Method using multiplication Solving systems of equations using the Elimination Method
Elimination using Addition Consider the system x - 2y = 5 Lets add both equations to each other 2x + 2y = 7 REMEMBER: We are trying to find the Point of Intersection. (x, y)
Elimination using Addition Consider the system x - 2y = 5 Lets add both equations to each other + 2x + 2y = 7 NOTE: We use the Elimination Method, if we can immediately cancel out two like terms.
Elimination using Addition Consider the system x - 2y = 5 Lets add both equations to each other + 2x + 2y = 7 3x = 12 x = 4 ANS: (4, y) NOTE: We use the Elimination Method, if we can immediately cancel out two like terms.
Elimination using Addition Consider the system x - 2y = 5 Lets substitute x = 4 into this equation. 2x + 2y = 7 4 - 2y = 5 Solve for y - 2y = 1 y = 1 2 ANS: (4, y) NOTE: We use the Elimination Method, if we can immediately cancel out two like terms.
Elimination using Addition Consider the system x - 2y = 5 Lets substitute x = 4 into this equation. 2x + 2y = 7 4 - 2y = 5 Solve for y - 2y = 1 1 2 y = 1 2 ANS: (4, ) NOTE: We use the Elimination Method, if we can immediately cancel out two like terms.
Elimination using Addition Consider the system 3x + y = 14 4x - y = 7 NOTE: We use the Elimination Method, if we can immediately cancel out two like terms.
Elimination using Addition Consider the system 3x + y = 14 + 4x - y = 7 7x = 21 x = 3 ANS: (3, y)
Elimination using Addition Consider the system 3x + y = 14 Substitute x = 3 into this equation 4x - y = 7 3(3) + y = 14 9 + y = 14 y = 5 ANS: (3, ) 5 NOTE: We use the Elimination Method, if we can immediately cancel out two like terms.
Examples… 1. 2. ANS: (4, -3) ANS: (-1, 2)
Elimination using Multiplication Consider the system 6x + 11y = -5 6x + 9y = -3
Elimination using Multiplication Consider the system 6x + 11y = -5 + 6x + 9y = -3 12x + 20y = -8 When we add equations together, nothing cancels out
Elimination using Multiplication Consider the system 6x + 11y = -5 6x + 9y = -3
Elimination using Multiplication Consider the system -1 ( ) 6x + 11y = -5 6x + 9y = -3
Elimination using Multiplication Consider the system - 6x - 11y = 5 + 6x + 9y = -3 -2y = 2 y = -1 ANS: (x, ) -1
Elimination using Multiplication Consider the system 6x + 11y = -5 6x + 9y = -3 Lets substitute y = -1 into this equation y = -1 6x + 9(-1) = -3 6x + -9 = -3 +9 6x = 6 x = 1 ANS: (x, ) -1
Elimination using Multiplication Consider the system 6x + 11y = -5 6x + 9y = -3 Lets substitute y = -1 into this equation y = -1 6x + 9(-1) = -3 6x + -9 = -3 +9 6x = 6 x = 1 ANS: ( , ) 1 -1
Elimination using Multiplication Consider the system x + 2y = 6 Multiply by -3 to eliminate the x term 3x + 3y = -6
Elimination using Multiplication Consider the system -3 ( ) x + 2y = 6 3x + 3y = -6
Elimination using Multiplication Consider the system -3x + -6y = -18 + 3x + 3y = -6 -3y = -24 y = 8 ANS: (x, 8)
Elimination using Multiplication Consider the system x + 2y = 6 Substitute y = 8 into equation 3x + 3y = -6 y =8 x + 2(8) = 6 x + 16 = 6 x = -10 ANS: (x, 8)
Elimination using Multiplication Consider the system x + 2y = 6 Substitute y = 8 into equation 3x + 3y = -6 y =8 x + 2(8) = 6 x + 16 = 6 x = -10 ANS: ( , 8) -10
Examples 1. 2. x + 2y = 5 x + 2y = 4 2x + 6y = 12 x - 4y = 16 ANS: (3, 1) ANS: (8, -2)
More complex Problems Consider the system 3x + 4y = -25 Multiply by 2
More complex Problems Consider the system 2( ) 3x + 4y = -25 -3( ) 2( ) 3x + 4y = -25 -3( ) 2x - 3y = 6
More complex Problems + Consider the system 6x + 8y = -50 ANS: (x, -4)
More complex Problems Consider the system 3x + 4y = -25 2x - 3y = 6 Substitute y = -4 2x - 3(-4) = 6 2x - -12 = 6 2x + 12 = 6 2x = -6 x = -3 ANS: (x, -4)
More complex Problems Consider the system 3x + 4y = -25 2x - 3y = 6 Substitute y = -4 2x - 3(-4) = 6 2x - -12 = 6 2x + 12 = 6 2x = -6 x = -3 ANS: ( , -4) -3
Examples… 2. 1. 2x + 3y = 1 4x + y = 9 5x + 7y = 3 3x + 2y = 8 ANS: (2, 1) ANS: (2, -1)