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Systems of Equations: Graphing. Unit 10, Day 4. Method 2: Substitution. Another method for solving a system of equations is called “Substitution”. Steps to Solving:. Solve one equation for one variable Substitute the expression from step one into the other equation.
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Systems of Equations:Graphing Unit 10, Day 4
Method 2: Substitution • Another method for solving a system of equations is called “Substitution”.
Steps to Solving: • Solve one equation for onevariable • Substitute the expression from step one into the other equation. • Simplify and solve the equation. • Substitute back into either original equation to find the value of the other variable. teachers.henrico.k12.va.us/math/.../3-2/3-2SolvSysSubst.ppt
Example #1: y = 4x 3x + y = -21 Step 1:Solve one equation for one variable. y = 4x Step 2: Substitute into the other equation. 3x+ 4x = -21 Step 3: Simplify and solve the equation. 7x = -21 x = -3 Step 4: Find the value of the other variable. 3(-3) + y = -21 -9 + y = -21 y = -12 Solution to the system is (-3, -12) teachers.henrico.k12.va.us/math/.../3-2/3-2SolvSysSubst.ppt
Example #2: x + y = 10 5x – y = 2 Step 1: Solve one equation for one variable. x + y = 10 y = 10- x Step 2: Substitute into the other equation. 5x -(10 - x) = 2 Step 3: Simplify and solve the equation. 5x -10 + x = 2 6x -10 = 2 6x = 12 x = 2 teachers.henrico.k12.va.us/math/.../3-2/3-2SolvSysSubst.ppt
Example #2: x + y = 10 5x – y = 2 Step 4: Substitute to find the value of the other variable. x + y = 10 2 + y = 10 y = 8 Solution to the system is (2,8). teachers.henrico.k12.va.us/math/.../3-2/3-2SolvSysSubst.ppt
Solve by substitution: 1. teachers.henrico.k12.va.us/math/.../3-2/3-2SolvSysSubst.ppt
Solve by substitution: 2. teachers.henrico.k12.va.us/math/.../3-2/3-2SolvSysSubst.ppt