The line 3x+y=0 may be perpendicular to one of the line given by ax2+2hxy+by2=0
Auxiliary equation=bm2+2hm+a=0⟶(1)3x+y=0
slope(m1)=−3
Hence slope of the line perpendicular to given line.
∴ Slope of one of the lines represented by the joint equation is 13.
Now 13 must be one of the roots of equation
b(13)2+2h(13)+a=0b19+2h3+0
b+6h+9a=0(The required condition)