Draw the graphs of the equations $x – y + 1 = 0$ and $3x + 2y -12 = 0$. Determine the coordinates of the vertices of the triangle formed by these lines and the x-axis, and shade the triangular region.

Given:

The given equations are:

$x-y+1=0$

$3x+2y-12=0$

To do:

We have to find the coordinates of the vertices of the triangle formed by the given straight lines and the x-axis. Also, we have to calculate the area formed by the triangle so formed.

Solution:

To represent the above equations graphically we need at least two solutions for each of the equations.

For equation $x-y+1=0$,

$y=x+1$

If $x=-1$ then $y=-1+1=0$

If $x=2$ then $y=2+1=3$

$x$	$-1$	$2$
$y$	$0$	$3$

For equation $3x+2y-12=0$,

$2y=12-3x$

$y=\frac{12-3x}{2}$

If $x=4$ then $y=\frac{12-3(4)}{2}=\frac{12-12}{2}=0$

If $x=2$ then $y=\frac{12-3(2)}{2}=\frac{12-6}{2}=\frac{6}{2}=3$

$x$	$4$	$2$
$y$	$0$	$3$

The equation of x-axis is $y=0$.

The above situation can be plotted graphically as below:

The lines AB, CD and AC represent the equations $x-y+1=0$, $3x+2y-12=0$ and x-axis respectively.

As we can see, the points of intersection of the lines AB, CD and AC taken in pairs are the vertices of the given triangle.

Hence, the vertices of the given triangle are $(-1,0), (2,3)$ and $(4,0)$. 

We know that,

Area of a triangle$=\frac{1}{2}bh$

In the graph, the height of the triangle is the distance between point B and AC.

Height of the triangle$=3$ units.

The base of the triangle$=$Distance between the points A and C.

The base of the triangle$=1+4=5$ units.

Area of the triangle formed by the given lines and x-axis$=\frac{1}{2}\times3\times5$

$=\frac{15}{2}$ sq. units. 

The area bounded by the given lines and x-axis is $7.5$ sq. units.