If the area of ABC with vertices A(x, y), B(1 , 2) and C (2,1) is 6sun

1.	If the area of ABC with vertices A(x, y), B(1 , 2) and C (2,1) is 6sunits then prove that x+y 15 or x ty+9 0[CBSE 2013
Answer» Given , x1=x y1 =y, x2=1,y2=2, x3=2, y3=1area= 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 proved and X+y=9

If the area of ABC with vertices A(x, y), B(1 , 2) and C (2,1) is 6sunits then prove that x+y 15 or x ty+9 0[CBSE 2013

Answer»

Given , x1=x y1 =y, x2=1,y2=2, x3=2, y3=1area= 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 proved

and X+y=9