If a, h, b are in A.P. then the triangle area formed by the pair of lines ax2+2hx+by2=0 and the line x−y=−2 in square units is
a+ba−b
a2+b2a−b
a−ba+b
a2+b2a+b
a, h, b are in A.P
2h=a+b, l=1,m=−1,n=2
n2h2−abam2−2hlm+bl2