Question icon
Algebra

The quadratic equation p(x) = 0 with real coefficient has purely imaginary roots.Then the equation p(p(x)) = 0 has
​1)only purely imaginary roots
2)all real roots
3)two real and two purely imaginary roots
4)neither real nor purely imaginary roots
Please explain the question and its solution..

Profile image of Meghendra Agrawal
7 Years agoGrade
Answers icon

2 Answers

Profile image of Aditya Gupta
7 Years ago
let p(x)=ax^2+bx+c........(1)
then p(p(x))= ay^2+by+c, where y=p(x)........(2)
now, let us assume that (2) has a real root ‘z’. as ‘z’ is real, p(z) is also real. that means (1) will have a real solution with x=p(z). but it is given that p(x) has  purely imaginary roots. so, p(p(x))=0 will have only purely imaginary roots.
option 1) is right
Profile image of Aditya Gupta
7 Years ago
actually, the roots will not be PURELY imaginary. they will be complex numbers, neither purely real nor purely imaginary