Please answer this question.................

Dear Student,

I n e q u a t i o n, A x^{2} + B x + C = 0 f o r r e a l a n d e q u a l r o o t s . B^{2} = 4 A C I n o u r c a s e, A = (a^{2} + b^{2}) B = - 2 (a c + b d) C = c^{2} + d^{2} {[- 2 (a c + b d)]}^{2} = 4 (a^{2} + b^{2}) (c^{2} + d^{2}) 4 (a^{2} c^{2} + b^{2} d^{2} + 2 a b c d) = 4 (a^{2} c^{2} + a^{2} d^{2} + b^{2} c^{2} + b^{2} d^{2}) 2 a b c d = a^{2} d^{2} + b^{2} c^{2} a^{2} d^{2} + b^{2} c^{2} - 2 a b c d = 0 {(a d - b c)}^{2} = 0 a d - b c = 0 a d = b c

Regards!