Question 80·Medium·Linear Equations in Two Variables
A map uses an -coordinate grid. In the graph shown, a straight river is represented by line , and a rescue boat is located at point .
The boat will travel along a straight path that passes through and is perpendicular to line . Which choice gives an equation of the boat’s path?
When a graph gives a line and asks for an equation of a related line, first compute the given line’s slope from two clear points. For perpendicular lines, switch to the negative reciprocal slope. Then plug the required point into (or point-slope form) to determine the intercept and match the result to a choice.
Hints
Read two points on line
Use the two marked points on line to compute its slope with .
Perpendicular slope rule
If a line has slope , any perpendicular line has slope (negative reciprocal).
Use point to find
After you know the slope, substitute the coordinates of into to solve for .
Desmos Guide
Plot the given points
Enter the points , , and .
Confirm the slope of line
Compute the slope with
to verify it is .
Use the perpendicular slope
Take the negative reciprocal of to get the perpendicular slope, .
Test answer choices by graphing
Graph each answer choice and see which one passes through and is perpendicular to the line through and . The correct equation is the one that satisfies both conditions.
Step-by-step Explanation
Find the slope of line
From the graph, line passes through and . The slope is
Use the perpendicular slope and point
A line perpendicular to slope has slope (the negative reciprocal).
Using point in with :
Write the equation
With and , the boat’s path is