Use the substitution method to solve the system x equals y minus 4, x + 8y = 2

Negative 3 1/3, 2/3
2/3, -3 and 1/3
Infinite solutions
No solutions

1 answer

To solve the system of equations using the substitution method, we'll start with the two equations given:

  1. \( x = y - 4 \)
  2. \( x + 8y = 2 \)

Now, we can substitute the expression for \( x \) from the first equation into the second equation.

Substituting \( x \) in the second equation:

\[ (y - 4) + 8y = 2 \]

Now, simplify the equation:

\[ y - 4 + 8y = 2 \]

Combine like terms:

\[ 9y - 4 = 2 \]

Now, add 4 to both sides:

\[ 9y = 6 \]

Divide both sides by 9:

\[ y = \frac{6}{9} = \frac{2}{3} \]

Now, we can find \( x \) using the first equation \( x = y - 4 \):

\[ x = \frac{2}{3} - 4 \]

To subtract, it's helpful to convert 4 into a fraction:

\[ x = \frac{2}{3} - \frac{12}{3} = \frac{2 - 12}{3} = \frac{-10}{3} \]

So we have found:

\[ x = -\frac{10}{3}, \quad y = \frac{2}{3} \]

Thus the solution to the system of equations is:

\[ \left( -\frac{10}{3}, \frac{2}{3} \right) \]

Reviewing the provided answer choices:

  • Negative 3 1/3, 2/3
  • 2/3, -3 and 1/3
  • Infinite solutions
  • No solutions

The correct answer, matching our solution, is:

Negative 3 1/3, 2/3 (equivalently, \( -\frac{10}{3}, \frac{2}{3} \)).