Let us considered two lines p1 and p2 and now we find the point of intersection.
The equation of lines are
a1x + b1y + c1 = 0
a2x + b2y + c2 = 0
Now let us assume that the point of intersection is (x0, y0)
So,
a1x0 + b1y0 + c1 = 0
a2x0 + b2y0 + c2 = 0
Using the Cramer's rule we get,
x0/(b1c2 - b2c1) = -y0/(a1c2 - a2c1) = 1/(a1b2 - a2b1)
Hence the point of intersection is
(x0, y0) = (b1c2 - b2c1/a1b2 - aq2b1, c1a2 - c2a1/a1b2 - a2b1)
So this is how we can find the intersecting lines
Angle of Intersection
Now we find the angle of intersection. So, the equation of the two lines in the slope intercept form are:
y = (-a1/b1)x + (c1/b1) = m1x + C1
y = (-a2/b2)x + (c2/b2) = m2x + C2
So,
tan θ = tan(θ2 - θ1) = tanθ2 - tanθ1/1 + tanθ1tanθ2 = m2 - m1/1 + m1m2
Given lines: y = 4x + 8 and y = 3x + 9
At the point of intersection both the lines have same point of intersection so
4x + 8 = 3x + 9
4x -3x = 9 - 8
x = 1
Now put the value of x in any of the above equation we get
y = 4 + 8
y = 12
So the intersection point is (1, 12)
No, such lines don't satisfy the criteria of intersecting lines, instead of above all are the characteristics of parallel lines. So, we can call the above lines parallel instead of intersecting lines.