The possible ordered pairs whose product will be negative (less than zero) are,

That is all these products will give us,


The point must be in the second quadrant where x is negative and y is positive.
Or in the fourth quadrant, where y is negative and x is positive.
For this case we have that by definition, the density is given by:

Where:
M: It is the mass of the diamond
V: It is the volume of the diamond
According to the data of the statement we have:

So the volume is:

Thus, the volume of the diamond is approximately 
Answer:

Constants are 4,3. The coefficient is 4.
X^2-10x+25 = (x-5)^2 or (x-5)(x-5)