Answer:
-8
Step-by-step explanation:
First we need to find the slope of CD.
We know C is (-10, -2)
and we know D is (10,6)
If we use the slope formula, we can see the slope is 
We can see point F is at (6,-4)
We can find the equation of this line by using point slope form, and plugging in F as our point.
To find where E, we need to find the y value when x = -4
A petri dish is simply a circle; thus, we use the formula of the area of the circle which is <span>πr^2.
Given r = 40 mm
A = </span>π(40)^2 = <span>5026.55 sq. mm
</span>
Population density = bacteria count / area
PD = 2,100 / <span>5026.55
PD = </span><span>0.417782 bacteria / mm sq.
Therefore, the answer is approximately 0.418 </span><span>bacteria per square millimeter.</span>
