dr. fowler ccm solving systems of equations by elimination – harder
TRANSCRIPT
Dr. Fowler CCM
Solving Systems of EquationsBy Elimination – Harder
Solving a system of equations by elimination using addition and subtraction.
Step 1: Put the equations in Standard Form.
Step 2: Determine which variable to eliminate.
Step 3: Add or subtract the equations.
Step 4: Plug back in to find the other variable.
Step 5: Check your solution.
Standard Form: Ax + By = C
Look for variables that have the
same coefficient.
Solve for the variable.
Substitute the value of the variable
into the equation.
Substitute your ordered pair into
BOTH equations.
ALREADY IN NOTES – Read Only for Review
Elimination using Multiplication
1) Solve the system. Adding or subtracting will not eliminate
x + 2y = 6
3x + 3y = -6
But, we can multiply the first equationby -3 to eliminate the x term
Elimination using Multiplication
x + 2y = 6
3x + 3y = -6
-3 ( )
1) Solve the system.
Elimination using Multiplication
-3x + -6y = -18
3x + 3y = -6+-3y = -24
y = 8
ANS: (x, 8)
Be sure to distribute the -3to ALL in the equation.
1) Solve the system.
Elimination using Multiplication
x + 2y = 6
3x + 3y = -6
ANS: (x, 8)
Substitute y = 8 into equation
y =8
x + 2(8) = 6x + 16 = 6
x = -10
1) Solve the system.
Elimination using Multiplication
x + 2y = 6
3x + 3y = -6
Answer: ( -10 , 8)
Substitute y = 8 into equation
y =8x + 2(8) = 6
x + 16 = 6
x = -10
1) Solve the system.
2) Solve the system:
2(2) + 2y = 6
4 + 2y = 6
2y = 2
y = 1
2x + 2y = 6
3x – y = 5
If we multiply the bottom
equation by 2 we can eliminate y:
2x + 2y = 6
(2)(3x – y = 5) 2x + 2y = 6(+) 6x – 2y = 10 8x = 16 x = 2
(2, 1)
Substitute x = 2 into either original equation:
More complex Problems
3x + 4y = -25
2x - 3y = 6
Multiply by 2
Multiply by -3.
This will get X’s to MATCH
3) Solve the system
More complex Problems
3x + 4y = -25
2x - 3y = 6
2( )
-3( )
3) Solve the system
More complex Problems
6x + 8y = -50
-6x + 9y = -18+17y = -68
y = -4
Answer: (x, -4)
3) Solve the system
More complex Problems
3x + 4y = -25
2x - 3y = 6 Substitute y = -4
2x - 3(-4) = 62x - -12 = 6
2x + 12 = 6
2x = -6
x = -3 Answer: (-3, -4)
3) Solve the system
3x + 4y = -14x – 3y = 7
4) Solve the system using elimination.
3(1) + 4y = -1
3 + 4y = -1
4y = -4
y = -1
Multiply both equations
(3)(3x + 4y = -1)
(4)(4x – 3y = 7)
9x + 12y = -3 (+) 16x – 12y = 28
25x = 25 x = 1
(1, -1)
Excellent Job !!!Well Done
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