Which of the following represents the zeros of f(x) = 6x3 - 31x2 + 4x + 5?
-5, one third , one half
5, -one third , one half
5, one third , -one half
5, one third , one half
Solution:
Given, f(x) = 6x3 - 31x2 + 4x + 5
We have to find the zeros of the quadratic function.
By rational root test,
The factors of the leading coefficient are 1, 2, 3, 6
The factors of the trailing constant are 1, 5
So, (x - 5) is a factor.
By long division,
The factor of 6x2 - x - 1 = 6x2 - 3x + 2x - 1
= 3x(2x - 1) + 1(2x - 1)
= (3x + 1)(2x -1)
So, x - 5 = 0
⇒ x = 5
3x + 1 = 0
3x = -1
⇒ x = -1/3
2x - 1 = 0
2x = 1
⇒ x = 1/2
Therefore, 5, -1/3 and 1/2 are the zeros of the function.
Which of the following represents the zeros of f(x) = 6x3 - 31x2 + 4x + 5?
Summary:
5, -1/3 and 1/2 represents the zeros of f(x) = 6x3 - 31x2 + 4x + 5.
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