JEE Main201911 Jan 2019Evening ShiftMathematicsQuadratic EquationActual
Let and be the roots of the quadratic equation x² -x( +1)+ =0 (0 < < 45^ ), and < . Then _ n=0 ^ ( ^ n + (-1)^ n ^ n ) is equal to :
Options
- A1 1- - 1 1+
- B1 1+ + 1 1-
- C1 1- + 1 1+
- D1 1+ - 1 1-
Correct answer
C. 1 1- + 1 1+
Step-by-step solution
x² -x( +1)+ =0 . x² -x -x+ =0x (x- )-1(x- )=0(x- )(x -1)=0 x= , cosec , (0,45^ ) = , = cosec _ n=0 ^ ^ n =1+ + ² + = 1 1- _ n=0 ^ (-1)^ n ^ n =1- 1 cosec + 1 cosec ² - 1 cosec ³ + =1- + ² - ³ + = 1 1+ _ n=0 ^ ( ^ n + (-1)^ n ^ n )= _ n=0 ^ ^ n + _ n=0 ^ (-1)^ n ^ n = 1 1- + 1 1+ .