Find an equation of a line with a slope of -1 and having the point $(-2,-6)$ on the line. Then graph it.

Verified Answer :

  • Start with the point-slope formula \(y - y_1 = m(x - x_1)\) using \(m = -1\) and \((-2, -6)\).
  • Substitute the values to get \(y + 6 = -1(x + 2)\).
  • Simplify to slope-intercept form to find the final equation: \(y = -x - 8\).
  • The graph is a line passing through \((-2, -6)\), \((0, -8)\), and \((-8, 0)\).
  • Final Answer: \(\boxed{y = -x - 8}\)

Explanation

  1. Formulating the Linear Equation

To find the equation of a line, we identify its given properties: the slope \(m = -1\) and a point \(P = (-2, -6)\) through which it passes. The point-slope form of a linear equation is a powerful tool here:
\[y - y_1 = m(x - x_1)\]
where \((x_1, y_1)\) is the given point. Substituting the known values, we have:
\[y - (-6) = -1(x - (-2))\]
\[y + 6 = -1(x + 2)\]

  1. Converting to Slope-Intercept Form

To simplify the equation into the slope-intercept form, \(y = mx + b\), we solve for \(y\):
\[y + 6 = -x - 2\]
Subtracting \(6\) from both sides:
\[y = -x - 2 - 6\]
\[y = -x - 8\]
This is the equation of the line. The slope is \(-1\) and the y-intercept is \(-8\).

  1. Graphing the Line

To visualize the line, we identify a few key points:

  • The given point: \((-2, -6)\)
  • The y-intercept: Setting \(x = 0\), we get \(y = -0 - 8 = -8\). So, the point is \((0, -8)\).
  • The x-intercept: Setting \(y = 0\), we get \(0 = -x - 8\), so \(x = -8\). The point is \((-8, 0)\).

By plotting these points on a coordinate plane and drawing a straight line through them, we represent the linear relationship defined by \(y = -x - 8\).

Examples

This linear relationship can model real-world scenarios where something decreases at a constant rate. For example, if you have a balance of \$8 in a savings account and withdraw \$1 every day, your balance \(y\) after \(x\) days could be represented by the equation \(y = -1x + 8\). In our case, the negative slope indicates a steady decline over time. Understanding such relationships helps in budget planning, tracking consumption, or predicting how resources deplete over time.