Math Problem Statement

If the points (-3, 5), (x, y) and (-2, 3) lie on a straight line, then what is the equation of the line?

Solution

To find the equation of the line that passes through the points (3,5)(-3, 5), (x,y)(x, y), and (2,3)(-2, 3), follow these steps:

1. Calculate the slope between two points

First, calculate the slope (mm) of the line using the points (3,5)(-3, 5) and (2,3)(-2, 3). The formula for the slope between two points (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) is:

m=y2y1x2x1m = \frac{y_2 - y_1}{x_2 - x_1}

Substitute the coordinates (x1,y1)=(3,5)(x_1, y_1) = (-3, 5) and (x2,y2)=(2,3)(x_2, y_2) = (-2, 3) into the formula:

m=352(3)=22=1m = \frac{3 - 5}{-2 - (-3)} = \frac{-2}{-2} = 1

So, the slope mm is 11.

2. Use the slope-point form to find the equation of the line

Now that we have the slope m=1m = 1, we can use the point-slope form of the equation of a line, which is:

yy1=m(xx1)y - y_1 = m(x - x_1)

Substitute the slope m=1m = 1 and the coordinates of one of the points, say (3,5)(-3, 5), into the equation:

y5=1(x(3))y - 5 = 1(x - (-3))

Simplify the equation:

y5=x+3y - 5 = x + 3

y=x+8y = x + 8

3. Verify the equation with the second point

We found the equation y=x+8y = x + 8. To verify, substitute the second point (2,3)(-2, 3) into this equation:

3=2+83 = -2 + 8

3=63 = 6

This result seems incorrect, meaning an error occurred. Let's re-evaluate the slope calculation and equation.

4. Re-calculate the correct slope and line equation

The previous steps revealed a possible miscalculation, so let's find the slope again between (3,5)(-3, 5) and (2,3)(-2, 3):

m=352(3)=21=2m = \frac{3 - 5}{-2 - (-3)} = \frac{-2}{1} = -2

Now, using point-slope form with this corrected slope:

y5=2(x+3)y - 5 = -2(x + 3)

Simplify the equation:

y5=2x6y - 5 = -2x - 6

y=2x1y = -2x - 1

5. Verify with the second point

Substituting (2,3)(-2, 3) into y=2x1y = -2x - 1:

3=2(2)1=41=33 = -2(-2) - 1 = 4 - 1 = 3

This matches, confirming that the correct equation of the line is:

y=2x1\boxed{y = -2x - 1}

Would you like further details or have any other questions?

Here are 5 related questions to explore further:

  1. How do you determine if three points lie on the same straight line?
  2. What is the general form of the equation of a line?
  3. How do you find the equation of a line parallel to a given line through a specific point?
  4. What is the relationship between the slopes of perpendicular lines?
  5. How can you derive the equation of a line from its slope and a point?

Tip: Always double-check your slope calculations and use a consistent approach to verify the correctness of your linear equations.

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Linear Equations

Formulas

Slope formula
Point-slope form of a line equation

Theorems

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Suitable Grade Level

Grades 7-9