Answer:

Step-by-step explanation:
Given

Required
Determine the roots
To get the root of the function, then f(b) must be 0;
i.e. f(b) = 0
So, the expression becomes

Add 75 to both sides


Take square roots of both sides


Reorder

Expand 75 as a product of 25 and 3

Split the expression




The options are not clear enough; however the roots of the equation are 
Scalene triangles. I think
This is the product of the square of a binomial expression. Therefore, it will have two factors.
Square of a binomial: a² + 2ab + b² = (a+b)²
The process:
9x² + 24x + 16
= (3x)² +2(3x)(4) + (4)²
= (3x + 4)² or (3x+4)(3x+4)
I hope this helps :)
The third one is correct.....so go for it without hesitation