Big Ideas Math Integrated I, 2016
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Big Ideas Math Integrated I, 2016 View details
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Exercise 3 Page 267

Does either of the equations have an isolated variable in it?

Infinitely many solutions

Practice makes perfect

In this system of equations, at least one of the variables has a coefficient of 1. Therefore, we will approach its solution with the Substitution Method. When solving a system of equations using the Substitution Method, there are three steps.

  1. Isolate a variable in one of the equations.
  2. Substitute the expression for that variable into the other equation and solve.
  3. Substitute this solution into one of the equations and solve for the value of the other variable.

For this exercise, y is already isolated in one equation, so we can skip straight to solving!

y=4x+4 & (I) -8x+2y=8 & (II)
y=4x+4 -8x+2( 4x+4)=8
y=4x+4 -8x+8x+8=8
y=4x+4 8=8 ✓

Solving this system of equations resulted in an identity; 8 is always equal to itself. Therefore, the lines are the same and have infinitely many intersection points.