Chapter 1: Problem 9
Plot the following points on graph paper: $$ \mathrm{P}(4,0), \mathrm{Q}(-2,9), \mathrm{R}(5,8), \mathrm{S}(-1,-2) $$ Hence find the coordinates of the point of intersection of the line passing through \(\mathrm{P}\) and \(\mathrm{Q}\), and the line passing through \(\mathrm{R}\) and \(\mathrm{S}\).
Short Answer
Expert verified
The intersection point is \(-2, 9)\.
Step by step solution
01
- Plot Point P(4,0)
Locate the point \(4,0\) on the graph paper. This point is on the x-axis, 4 units to the right of the origin.
02
- Plot Point Q(-2,9)
Locate the point \(-2, 9\) on the graph paper. This point is 2 units to the left of the origin on the x-axis and 9 units up on the y-axis.
03
- Plot Point R(5,8)
Locate the point \(5,8\) on the graph paper. This point is 5 units to the right on the x-axis and 8 units up on the y-axis.
04
- Plot Point S(-1,-2)
Locate the point \(-1,-2\) on the graph paper. This point is 1 unit to the left on the x-axis and 2 units down on the y-axis.
05
- Draw Line PQ
Draw a straight line passing through points \(4,0\) and \(-2,9\).
06
- Draw Line RS
Draw a straight line passing through points \(5,8\) and \(-1,-2\).
07
- Find the Intersection
Calculate the intersection of the lines. Find the equations of the lines to solve for the intersection point. For line \(PQ\): \[ \frac{y-0}{9-0} = \frac{x-4}{-2-4} \] simplifying, we get: \[ y = -\frac{3}{2}x + 6 \] For line \(RS\): \[ \frac{y-8}{-2-8} = \frac{x-5}{-1-5} \] simplifying, we get: \[ y = \frac{10}{6} x - \frac{10}{6}(5) + 8 = \frac{5}{3}x - \frac{34}{3} \] Equate the two line equations to find the intersection point: \[ -\frac{3}{2}x + 6 = \frac{5}{3}x - \frac{34}{3} \] Solve for \(x\), then substitute back to find \(y\).
08
- Solve for x
Equate and solve the x-values: \[ -\frac{3}{2}x + 6 = \frac{5}{3}x - \frac{34}{3} \] Combining the terms: \[ -\frac{3}{2}x - \frac{5}{3}x = -\frac{130}{6} - 12 \] Simplifying, we get \[ x = -2 \].
09
- Solve for y
Substitute \(x = -2\) back into one of the line equations: \[ y = -\frac{3}{2} (-2) + 6 = 3 + 6 = 9 \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graph Plotting
Graph plotting involves placing points on a coordinate system. Each point has an x-coordinate (horizontal axis) and a y-coordinate (vertical axis). For instance, to plot point \(\text{P}(4,0)\), move 4 units to the right on the x-axis and stay at 0 on the y-axis. For point \(\text{Q}(-2,9)\), move 2 units to the left on the x-axis and 9 units up on the y-axis. Plotting correctly is crucial for visualizing relationships and solving problems. Remember:
- Start at the origin (0,0).
- Move horizontally to the x-coordinate.
- Move vertically to the y-coordinate.
Line Equations
A line equation represents all the points on a line. It is often written in the form \(y = mx + c\), where \m\ is the slope (steepness) of the line, and \c\ is the y-intercept (where the line crosses the y-axis). To find a line equation passing through two points:
- Calculate the slope: \(m = \frac{y_2 - y_1}{x_2 - x_1}\).
- Use one point to solve for the y-intercept \(c\).
- Combine these to write the equation.
Point of Intersection
The point of intersection is where two lines cross. To find this:
- First, get the equations of both lines.
- Set the equations equal to each other and solve for \x\.
- Substitute this \x\ value back into one of the equations to find the \y\ value.
Coordinate Systems
A coordinate system is a grid formed by two perpendicular lines: the x-axis (horizontal) and the y-axis (vertical). The point where they intersect is the origin \((0,0)\). The coordinate system divides the plane into four quadrants, helping locate points. Each point is represented as \((x,y)\):
- The first number is the x-coordinate (horizontal position).
- The second is the y-coordinate (vertical position).