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Warm Up Solve using substitution. 1. y = 2x –1 and 2x + y = 3 2. x = y + 3 and 2x – y = 5 3. y = -6x – 2 and 12x + 2y = -6 Answers 1. (1, 1) 2. (2, -1) 3. No solution Lesson 7.3B Solving systems of equations using substitution 5 Simple Steps To finding the Solution: Solve one equation for either x or y Substitute the expression into the other equation Solve for the variable Substitute the value back in and solve Check your answer, is it a solution? Remember that a point consists of an “x” value and a “y” value. You have to find BOTH to find the solution! S’more Practice… Solve the following system of equations. 1. 2x + y = 12 Hint: y + 3x = 23 You must pick one equation to solve for a single variable so that you can substitute it into the other equation! (11, -10) Example 2: -6x – 8y = 4 6x + 6y = -6 (-2, 1) Example 3: 2x + 2y = -16 4x – 4y = 32 (0, -8) Class Activity: Substitution Revolution! Your teacher will pass out a note card to each of you. Once you have your note card, write down an equation in 2 variables (Ex. y =-3x +9). The equation can be anything you want, but please keep the numbers in front of the variables between -6 and 6. When everyone has their equation break into 2 lines and begin substituting with the person across from you (this means everyone should have a sheet of lined paper out to show your work and turn into your teacher at the end of class). Once everyone is done solving the revolution begins…and you will substitute your equation with the next person across from you! Summary: Explain why it is important to keep the expression you substitute into the other equation wrapped in parentheses. Homework: Worksheet 7.3B