JEE Main201911 Jan 2019Morning ShiftMathematicsComplex NumberActual
Let (-2- 1 3 i )³= x+i y 27 (i= -1 ), where x and y are real numbers then y - x equals
Options
- A91
- B-85
- C85
- D-91
Correct answer
A. 91
Step-by-step solution
-(6+i)³=x+i y - [216+i³+18 i(6+i) ]=x+i y -[216-i+108 i-18]=x+i y -216+i-108 i+18=x+i y -198-107 i=x+i y x=-198, y=-107 y-x=-107+198=91