Find The Equation Of The Line In Standard Form Ax+By=C That Has A Slope Of (-1)/(6) And Passes Through
Understanding how to determine the equation of a straight line given a specific slope and a point it passes through is a fundamental concept in coordinate geometry. The standard form of a line’s equation, Ax + By = C, provides a concise way to represent lines and analyze their properties. In this article, we will explore how to derive the standard form of a line with a given slope and passing through a particular point, focusing on the slope of -1/6. We will break down the process step-by-step, illustrate with examples, and discuss various methods to arrive at the desired equation.
Understanding the Components of a Line Equation
What Is the Standard Form of a Line?
The standard form of a linear equation is written as:- Ax + By = C
where:
- A, B, and C are real numbers,
- A and B are not both zero,
- The coefficients are usually chosen to be integers with no common factors (for simplicity).
This form is particularly useful for quickly identifying intercepts, and for analyzing the relationship between x and y in a linear relationship.
What Is the Slope of a Line?
The slope (m) of a line indicates its steepness and direction. It is calculated as:- m = (change in y) / (change in x)
Given the slope m = -1/6, it means:
- For every 6 units moved horizontally to the right, the line drops 1 unit vertically.
- The line is decreasing from left to right.
Given Data and Objective
Suppose the line passes through a specific point, say, \( (x1, y1) \). Our goal is to find the equation of the line in standard form, Ax + By = C, that:
- Has a slope \( m = -\frac{1}{6} \),
- Passes through \( (x1, y1) \).
The process involves:
- Using the point-slope form of the line equation.
- Rearranging into standard form.
Method 1: Using the Point-Slope Form
Step 1: Write the Point-Slope Equation
The point-slope form of a line is:- y - y1 = m(x - x1)
Given:
- \( m = -\frac{1}{6} \),
- a point \( (x1, y1) \).
The equation becomes:
\[ y - y1 = -\frac{1}{6}(x - x1) \]
Step 2: Clear the Fraction
Multiply both sides by 6 to eliminate the denominator:\[ 6(y - y1) = - (x - x1) \]
which simplifies to:
\[ 6y - 6y1 = -x + x1 \]
Step 3: Rearrange into Standard Form
Bring all terms to one side:\[ x + 6y = x1 + 6 y1 \]
This is the line in standard form:
\[ Ax + By = C \]
where:
- \( A = 1 \),
- \( B = 6 \),
- \( C = x1 + 6 y1 \).
Note: If specific point coordinates are provided, substitute them into the above to find the exact C.
Method 2: General Approach with a Specific Point
Suppose the line passes through the point \( (x1, y1) = (2, 3) \). Let's find the equation step-by-step.
Step 1: Write the point-slope form
\[ y - 3 = -\frac{1}{6}(x - 2) \]
Step 2: Multiply through by 6 to clear fractions
\[ 6(y - 3) = -(x - 2) \]
\[ 6y - 18 = -x + 2 \]
Step 3: Rearrange to standard form
\[ x + 6y = 20 \]
This is the standard form of the line passing through (2, 3) with slope -1/6.
General Process for Any Point
If the point is \( (x1, y1) \), the general formula becomes:
\[ x + 6 y = x1 + 6 y1 \]
which directly provides the standard form once the specific point is substituted.
Additional Considerations
Ensuring the Standard Form is in the Correct Format
- Usually, A should be positive. If A is negative, multiply the entire equation by -1 to make A positive.
- Coefficients A, B, and C should be integers with no common factors for simplicity, if possible.
Example: Line Passing Through Multiple Points
Suppose you are asked to find the line passing through two points \( (x1, y1) \) and \( (x2, y2) \) with the given slope:- Find the slope between the two points.
- Confirm that it matches the given slope (-1/6).
- Use the point-slope form with either point.
- Convert to standard form.
Practice Problem and Solution
Problem: Find the equation of a line in standard form that has a slope of -1/6 and passes through the point \( (4, -2) \).
Solution:
- Write point-slope form:
\[ y - (-2) = -\frac{1}{6}(x - 4) \]
\[ y + 2 = -\frac{1}{6}x + \frac{4}{6} \]
\[ y + 2 = -\frac{1}{6}x + \frac{2}{3} \]
- Multiply through by 6:
\[ 6 y + 12 = -x + 4 \]
- Rearrange to standard form:
\[ x + 6 y = -12 + 4 \]
\[ x + 6 y = -8 \]
This is the standard form of the line.
Summary and Key Takeaways
- To find the equation of a line in standard form given a slope and a point, start with the point-slope form.
- Clear fractions by multiplying through by the denominator.
- Rearrange the resulting equation to the form Ax + By = C.
- Ensure the coefficients are simplified and A is positive.
Conclusion
Deriving the equation of a line in standard form from a given slope and point involves a systematic process that starts with the point-slope form, simplifies to eliminate fractions, and rearranges into the desired standard form. Mastery of this method enables students and mathematicians to quickly analyze line equations, find intersections, and solve geometric problems efficiently. Whether working with theoretical problems or practical applications, understanding these steps is essential for a solid foundation in analytic geometry.