High School

The line l_1 has equation 2x - 3y + k = 0, where k is a constant.

The point A (2, 3) lies on l_1, as shown.

Find:

(i) the value of k.

(ii) the slope of l_1.

Answer :

To solve this problem, we need to find both the value of the constant [tex]k[/tex] and the slope of the line [tex]l_1[/tex]. Let's address each part of the question step-by-step:

(i) Finding the value of [tex]k[/tex]:

The equation of the line [tex]l_1[/tex] is given as:

[tex]2x - 3y + k = 0[/tex]

We know that the point [tex]A(2, 3)[/tex] lies on this line. This means that when [tex]x = 2[/tex] and [tex]y = 3[/tex], the equation of the line should be satisfied.

Substitute [tex]x = 2[/tex] and [tex]y = 3[/tex] into the equation:

[tex]2(2) - 3(3) + k = 0[/tex]

Simplify the equation:

[tex]4 - 9 + k = 0[/tex]

Combine the numbers:

[tex]-5 + k = 0[/tex]

Solve for [tex]k[/tex] by adding 5 to both sides:

[tex]k = 5[/tex]

So, the value of [tex]k[/tex] is 5.

(ii) Finding the slope of [tex]l_1[/tex]:

The general form of the equation for a line is [tex]Ax + By + C = 0[/tex]. The slope [tex]m[/tex] of the line given by this equation can be calculated using the formula [tex]m = -\frac{A}{B}[/tex].

In this case, [tex]A = 2[/tex] and [tex]B = -3[/tex]. Therefore, the slope [tex]m[/tex] of the line [tex]l_1[/tex] is:

[tex]m = -\frac{2}{-3} = \frac{2}{3}[/tex]

Thus, the slope of [tex]l_1[/tex] is [tex]\frac{2}{3}[/tex].

In summary:


  1. The value of [tex]k[/tex] is 5.

  2. The slope of [tex]l_1[/tex] is [tex]\frac{2}{3}[/tex].