Question

Show graphically that the following system of equations is in-consistent (i.e. has no solution):

3x – 5y = 20

6x – 10y = – 40

Answer 1

The given equations are

3x - 5y = 20 ...(i)

6x - 10y = -4 ...(ii)

Putting x = 0 in equation (i)  we get

`=> 3 xx 0 - 5y = 20`

`=> y = -4`

x = 0, y = -4

Putting y = 0 in equation (i) we get

`=> 3x - 5 xx 0 = 20`

`=> x = 20/3`

`x = 20/3, y = 0`

Use the following table to draw the graph.

x	0	`20/3`
y	-4	0

Draw the graph by plotting the two points  A(0, -4), B`(20/3, 0)` from table

Graph of the equation ...(ii)

6x - 10y = -4 ....(ii)

Putting x = 0 in equaion (ii) we get

`=> 6 xx  0 - 10y = -4`

`=> y = 2/5`

`x = 2/5, y = 0`

Putting y = 0 in equation (ii) we get

`=> 6x - 10 xx 0 = -4`

`=> x = -2/3`

`x = -2/3, y = 0`

Use the following table to draw the graph.

x	0	`-2/3`
y	`2/5`	0

Draw the graph by plotting the two points C(0, -4), D`(20/3, 0)` from table.

Here we see that the two lines are parallel.

Hence the given system of equations has no solution.