Question

The course of an enemy submarine, as plotted on rectangular co-ordinate axes, gives the equation 2x + 3y = 4. On the same axes, a destroyer's course is indicated by the graph x - y = 7. Use the graphical method to find the point at which the paths of the submarine and the destroyer intersect?

Answer 1

2x + 3y = 4
⇒ x = `(4 - 3y)/(2)`
The table for 2x + 3y = 4 is

X	-1	-4	5
Y	2	4	-2

x - y = 7
⇒ x = y + 7
The table for x - y = 7 is

X	5	11	9
Y	-2	4	2

Now plot the points on a graph and we get the following required graph:

The point at which the paths of the submarine and the destroyer intersect are (5, -2)