# Section 3: solving Systems of Equations with combinations/elimination.

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Section 3: solving Systems of Equations with combinations/elimination

Review When is it easiest to solve a system of equations using the graphing method? When is it easiest to solve a system of equations using the substitution method?

Solve the System by Graphing y = 5x – 4 y = 2x - 1

Solve the System using Substitution x = 2y + 3 -4x + 5y = 6

Elimination/Combination Elimination/Combination is best used when both equations in the system are in standard form (Ax + By = C) This method combines both equations by adding or subtracting them together, but one of the variables must be eliminated as soon as the equations are combined.

Ex 1: Solve using Elimination/Combinations 4x – 2y = 7 x + 2y = 3 * are the equations in standard form?

Elimination/Combination – part 2 Review: Solve the system. 2x – 3y = 10 4x + 3y = 8

Example- Subtracting 4x+9y=1 4x+6y=-2

EX 2: Solve the System 2x – 3y = 6 -2x + 3y = -6 If 3x – 4y =12, can you write another equation to make the system no solutions?

Class Work Pg 126 # 18-23, 29

Ex 3: Solve the system using Elimination A. 4x + 9y = 2 B. -5x + 8y = 16 2x – 5y = 6 10x + 24y = 15

Ex 4: Solve using Elimination 3x + 7y = 15 5x + 2y = -4

HOMEWORK Eliminations Worksheet – 1 st column 2 nd column is bonus Eliminations Open Response #2