Question

 f(x) =(a sin x + b cos x)/(c sin x d cos x)  decreases for all x if - 

(A) ad – bc < 0 

(B) ad – bc > 0 

(C) ab – cd > 0 

(D) ab – cd < 0

Answer 1

Correct option (A) ad – bc < 0

Explanation: 

∵ f(x) is decreasing for all x if and only if f'(x) < 0 for all x 

∴ ad – bc < 0 ⇒ ad < bc