Verified Answer :

  • Determine the slope of the line passing through \((-5, -2)\) and \((-1, 4)\) using the formula \(m = \frac{y_2 - y_1}{x_2 - x_1}\), resulting in \(m = \frac{3}{2}\).
  • Use the point-slope form \(y - y_1 = m(x - x_1)\) to derive the equation \(y - 4 = \frac{3}{2}(x + 1)\).
  • Simplify to the slope-intercept form: \(y = \frac{3}{2}x + \frac{11}{2}\).
  • Express the final equation as: \(\boxed{y = \frac{3}{2}x + \frac{11}{2}}\).

Explanation

  1. Calculate the slope of the line.

To determine the equation of a line passing through two points, we first calculate its slope. Given two points \((x_1, y_1) = (-5, -2)\) and \((x_2, y_2) = (-1, 4)\), the slope \(m\) is defined as the ratio of the change in \(y\) to the change in \(x\):
\[m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{4 - (-2)}{-1 - (-5)} = \frac{6}{4} = \frac{3}{2}\]
The slope of the line is \(\frac{3}{2}\).

  1. Find the equation of the line.

Now that we have the slope \(m = \frac{3}{2}\), we can use the point-slope form of a linear equation, which is \(y - y_1 = m(x - x_1)\). Substituting the point \((-1, 4)\) into this form:
\[y - 4 = \frac{3}{2}(x - (-1))\]
\[y - 4 = \frac{3}{2}(x + 1)\]
\[y - 4 = \frac{3}{2}x + \frac{3}{2}\]
Adding \(4\) (or \(\frac{8}{2}\)) to both sides gives the slope-intercept form:
\[y = \frac{3}{2}x + \frac{3}{2} + \frac{8}{2}\]
\[y = \frac{3}{2}x + \frac{11}{2}\]
This is the equation of the line in slope-intercept form.

  1. Verify and express the final equation.

We can rewrite the equation in standard form \(Ax + By = C\) by multiplying by 2 and rearranging:
\[2y = 3x + 11\]
\[-3x + 2y = 11\]
\[3x - 2y = -11\]
To verify, check the points \((-5, -2)\) and \((-1, 4)\):

  • For \((-5, -2)\): \(3(-5) - 2(-2) = -15 + 4 = -11\) (Matches)
  • For \((-1, 4)\): \(3(-1) - 2(4) = -3 - 8 = -11\) (Matches)

The final equation of the line is \(\boxed{y = \frac{3}{2}x + \frac{11}{2}}\) or \(\boxed{3x - 2y = -11}\).

Examples

Understanding how to find the equation of a line is essential in fields like engineering and economics. For example, if you are tracking the linear growth of a project's cost relative to time, you can define two points \((time_1, cost_1)\) and \((time_2, cost_2)\) and use the linear equation to predict future costs. If your project starts at \(\$2000\) and grows at a steady rate, finding this line helps in budgeting for future months. Calculations like \(m = \frac{y_2 - y_1}{x_2 - x_1}\) become powerful tools for planning and forecasting.