about to only mathematics

Options

A. equilateral
B. right angled
C. scalene
D. none of these

Answer

D

Explanation

The given lines are
`(a+b)x+(a-b)y-2ab=0 " " (1)`
`(a-b)x+(a+b)y-2ab=0 " " (2)`
`"and " x+y=0 " " (3)`
Lines (1) and (2) are symmetrical about the line y=x (as on interchanging x and y in `1^(st)` line gives `2^(nd)` line).
So, y=x is one of the angle bisectors.
This is perpendicular to the third side x+y=0.
Therefore, triangle is isosceles.