Consider the straight line equation, x+3y−4=0,x+y−4=0 and 3x+y−4=0 The triangle formed will be,
So, x+2y−4=03x+y−4=03x+9y−12=0 For the point A intersection, 3x+y−4=0−−+−−−−−−−−−−−−−8y=8y=1 This implies, 3x+1−4=03x=3x=1 For the intersection point B, 3x+y−4=0x+y−4=0−−+−−−−−−−−−−−−−2y=0y=0 This implies, x=4 Similarly for point C, x=0,y=4 Then, the triangle formed will be,
Then, AB=9+1​=10​ And, BC=32​=42​ And, CA=10​ This implies, AB=CA So, the triangle ABC is an isosceles triangle.