Question

if the area of the triangle ABC formed by A(x,y),B(1,2) and C(2,1)is 6 square units,prove that x+y=15

Answer 1

given , x1=x y1 =y, x2=1,y2=2, x3=2, y3=1
area= 6 sq.units
area of triangle = 1/2 {x1(y2-y3)+x2(y3-y1)+x3(y1-y2)}
6=1/2{x(2-1)+1(1-y)+2(y-2)}
12=x+1-y+2y-4
12=x-3+y
12+3=x+y
15=x+y
hence prove

Answer 2

hence prooved...........