Question

Find a cubic polynomial with the sum, sum of the product of its zeroes is taken two at a time, and product of its zeroes as 3, -1 and -3 respectively.

Answer 1

Let the polynomial be ax3 + bx2 + cx + d and the zeroes be α, β and γ Then, α + β + γ = -(-2)/1 = 2 = -b/a αβ + βγ + γα = -7 = -7/1 = c/a αβγ = -14 = -14/1 = -d/a∴ a = 1, b = -2, c = -7 and d = 14 So, one cubic polynomial which satisfy the given conditions will be x3 - 2x2  - 7x + 14

Answer 2

$\huge\fbox \red{Solution:}$

Generally,

A cubic polynomial say, f(x) is of the form ax3 + bx2 + cx + d.

And, can be shown w.r.t its relationship between roots as.

⇒ f(x) = k [x3 – (sum of roots)x2 + (sum of products of roots taken two at a time)x – (product of roots)]

Where, k is any non-zero real number.

Here,

f(x) = k [x3 – (3)x2 + (-1)x – (-3)]

∴ f(x) = k [x3 – 3x2- x + 3)]

where, k is any non-zero real number.