If A(x1,y1) and B(x2,y2) be two points, then the equation of line will be,
(y−y1)=(y2−y1x2−x1)(x−x1)
Equation of AB,
y−4=(−3−4)(2−1)(x−1)
⇒ y−4=−7(x−1)
⇒ y−4=−7x+7
⇒ 7x+y−11=0
[1 Mark]
Equation of BC,
y+3=(−2+3)(−1−2)(x−2)
⇒ y+3=−13(x−2)
⇒ 3y+9=−x+2
⇒ x+3y+7=0
[1 Mark]
Equation of AC,
y−4=(−2−4)(−1−1)(x−1)⇒ y−4=3(x−1)⇒ y−4=3x−3⇒3x−y+1=0
[1 Mark]