I hope everyone is safe. I am Shivam Jadhav . I am year undergraduate currently studying Computer Science at IIT Delhi. I wish to start a series where I will discuss how to attack a math problem in JEE-Advanced . Because in JEE-advanced speed matters a lot especially for the MATH section .If I get a good response to this note , I will try to cover more topics .I will choose the topic for every week depending upon what you people want .
Complex Numbers is a topic covered under the syllabus of JEE-Mains as well as JEE-Advanced exam. Lots of questions are asked from this topic in both exams . Below are few problems on complex numbers and I present the solution how I would solve that particular problem . These question require basic properties of complex number. I will share some more question on complex number requiring different techniques. Before reading the solution try to solve it yourself so that you can check whether the method you used was efficient. I hope you all like it. If you like do reshare :)
Find the set
: Since the denominator is complex we try to make it real by multiplying by conjugate of denominator.
Also note that . Conjugate of denominator is . Multiplying numerator and denominator by
Now this implies so the set is
Don't try to put because it will consume a lot of time rather operate with
Let be a complex number such that the imaginary part of is not non-zero and is real . Then cannot take the value
is real implies .
using , we get but since implies . Hence we get .
(We don't need to look at complex part as it will be since is real ). Now substitute
and since can never be .
PS: Here I preferred using because the number of terms of are only two in the equation and they are which are easy to compute.
Let be a complex number where and are integers . Then the area of the rectangle whose vertices are the roots of the equation
substitute we get which gives .
So area of rectangle is
PS: If I had tried to substitute in the equation given in question then it would have been tedious to solve . So always try to simplify the expression in terms as long as you can and if you can't further simplify it then try to substitute .