What is the condition for the line lx+my+n=0lx + my + n = 0lx+my+n=0 to be a normal to the ellipse x2a2+y2b2=1\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1a2x2+b2y2=1?
a2l2+b2m2=(a2−b2)2n2\frac{a^2}{l^2} + \frac{b^2}{m^2} = \frac{(a^2-b^2)^2}{n^2}l2a2+m2b2=n2(a2−b2)2
a2l2+b2m2=n2a^2l^2 + b^2m^2 = n^2a2l2+b2m2=n2
l2a2+m2b2=1n2\frac{l^2}{a^2} + \frac{m^2}{b^2} = \frac{1}{n^2}a2l2+b2m2=n21
a2/l2−b2/m2=n2a^2/l^2 - b^2/m^2 = n^2a2/l2−b2/m2=n2