So, given a quadratic function, y = ax2<span> + bx + c, when "a" is positive, the </span>parabola<span> opens upward and the vertex is the </span>minimum<span> value. On the other hand, if "a" is negative, the graph opens </span>downward<span> and the vertex is the </span>maximum<span> value. To put it in complicated terms. Or when A is positive the graph is shaped like a U but if A is negative the graph is an upside down U
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Answer:

Step-by-step explanation:
The large mixing tank initially holds 500 gallons of water in which 50 pounds of salt have been dissolved.
Volume = 500 gallons
Initial Amount of Salt, A(0)=50 pounds
Brine solution with concentration of 2 lb/gal is pumped into the tank at a rate of 3 gal/min
=(concentration of salt in inflow)(input rate of brine)

When the solution is well stirred, it is then pumped out at a slower rate of 2 gal/min.
Concentration c(t) of the salt in the tank at time t
Concentration, 
=(concentration of salt in outflow)(output rate of brine)

Now, the rate of change of the amount of salt in the tank


We solve the resulting differential equation by separation of variables.

Taking the integral of both sides

Recall that when t=0, A(t)=50 (our initial condition)

Answer:
Follows are the solution to the given points:
Step-by-step explanation:
Given value:
For point a:
Moment generating function of X=?
Using formula:


integrating the values by parts:
Therefore, the moment value generating by the function is 
In point b:
Using formula:

form point (a):

Differentiating the value with respect of t

when

Factors of 21 are : 1,3,7,21....yes, this is correct...true