Question

if the area of triangle formed by points (a,0)(1,1)(0,2) is 4 sq.units find a

Answer 1

Area = 1/2 | x1(y2-y3) + x2(y3-y1) +x3(y1-y2) |
4 = 1/2 | a(-1) + 1(2) + 0(0-1) | 
8 = |-a+2|
2 - a = 8               or             2-a = -8a = -6                   or             a = 10