[tex]\displaystyle\bf\\A(1,4),~B(2,-3),~C(-1,-2)\\Equation~of~a~side~AB~is:\\\\\frac{x-B_x}{A_x-B_x}=\frac{y-B_y}{A_y-B_y}\\\\\\\frac{x-2}{1-2}=\frac{y-(-3)}{4-(-3)}\\\\\\\frac{x-2}{-1}=\frac{y+3}{7}\\\\\\7(x-2)=-1(y+3)\\\\7x-14=-y-3\\\\7x-14+y+3=0\\\\7x+y-14+3=0\\\\\boxed{\bf7x+y-11=0}[/tex]
