Answer:
1) p=1/2
2) V(p)=25
Explanation:
We have the function: 

Which represents the variance of the number of left handed people in a group of 100. 
Question 1) 
We want to find the value of p that maximizes the variance. 
Let's examine our function. We can see that it is a quadratic. Therefore, the value of p that maximizes the variance will simply be the x-coordinate of the vertex of our equation. 
Let's expand our function: 

Distribute: 

Let's find the vertex of our equation. We can use the following formulas (I switched out the x for p): 

Let's determine our coefficients. The "a" is the coefficient in front of the squared term and "b" is the coefficient in front of the x term. 
So, a is -100, and b is 100. 
Substitute them into our formula: 

Multiply: 

Divide: 

So, the x-coordinate (or rather p in this case) of our vertex is 1/2. 
To find the y-value, let's substitute it back into our function. We have: 

Substitute 1/2 for p: 

Evaluate: 

Therefore, our vertex is: 

So, the value of p that maximizes our variance is p=1/2. 
Question 2) 
We want to find the maximum variance. 
Again, this will simply be the vertex of our quadratic. 
This time, it will be the y-coordinate. 
We can see that the y-coordinate of the vertex is 25. 
So, our maximum variance is V(p)=25. 
And we're done!