UPSC NDA I and II 2020 Math Solved Paper

Equation of two sides of the triangle are x+2=0 and y+2=0
They intersect at right angle.
Thus, triangle formed by them is a right angle triangle. Circumcentre of the right triangle lies on its hypotaneous.
So, circumcentre (-1,-1) must lies on the line Kx+y+2=0
∴K(−1)+(−1)+2=0 ⇒K=1