In math class, Emma and Angelle pair as a group. Emma’s task is to graph (7/2)x–(9/2)= 2y and Angelle’s task is to graph 4y=7x–9. After they complete their graphs, they compare their work. They both get exactly the same graph. What is the solution of (7/2)x–(9/2)= 2y and 4y=7x–9?

1 answer

To find the solution of the equations \( \frac{7}{2}x - \frac{9}{2} = 2y \) and \( 4y = 7x - 9 \), we first need to examine both equations.

Let's manipulate the first equation:

  1. Start with: \[ \frac{7}{2}x - \frac{9}{2} = 2y \]

  2. Rearrange it to isolate \( y \): \[ 2y = \frac{7}{2}x - \frac{9}{2} \] Divide both sides by 2: \[ y = \frac{7}{4}x - \frac{9}{4} \]

Now, let's manipulate the second equation:

  1. Start with: \[ 4y = 7x - 9 \]

  2. Rearrange it to isolate \( y \): \[ y = \frac{7}{4}x - \frac{9}{4} \]

Now we have both equations in slope-intercept form:

  • From the first equation: \( y = \frac{7}{4}x - \frac{9}{4} \)
  • From the second equation: \( y = \frac{7}{4}x - \frac{9}{4} \)

Since both equations are the same, they represent the same line on a graph.

To find the solutions of the equation system, we can set the two expressions for \( y \) equal to each other, but since they are identical, we can find their intersections by plugging in any value of \( x \) to find the corresponding value of \( y \).

To find a particular solution, we can set \( x = 0 \):

  1. Substitute \( x = 0 \): \[ y = \frac{7}{4}(0) - \frac{9}{4} = -\frac{9}{4} \]

Thus, a specific point on the line is \( (0, -\frac{9}{4}) \).

Alternatively, let's find another point by setting \( y = 0 \):

  1. Set \( y = 0 \): \[ 0 = \frac{7}{4}x - \frac{9}{4} \]

  2. Rearranging this gives: \[ \frac{7}{4}x = \frac{9}{4} \] Multiplying by \( \frac{4}{7} \): \[ x = \frac{9}{7} \]

Now, we found two solutions:

  1. \( (0, -\frac{9}{4}) \)
  2. \( (\frac{9}{7}, 0) \)

The lines intersect infinitely at all points on the line \( y = \frac{7}{4}x - \frac{9}{4} \).

Thus, the solution set of the system of equations is represented by the line, or \( {(x, \frac{7}{4}x - \frac{9}{4}) : x \in \mathbb{R}} \).