KVPY SX SB Exam 20141 Question Paper

Question : 85 of 120

Marks: +1, -0

The number of integers n for which

3x^3 - 25x + n = 0

has three real roots is

Solution:

x(3x^2 - 25) = - n

3x(x^2-25/3)=-n

3x(x-√{25/3})(x+√{25/3})=-n

∴

n ∈ (-250/9,250/9)

∴ But n ∈ I
Total integer = 55

Go to Question:

Prev Question

Next Question