All AP Calculus AB Resources
Example Questions
Example Question #31 : Integrals
If what is ?
Taking the derivative of gives you .
Taking the derivative of gives you .
Finally taking the derivative of gives you .
Therefore .
Example Question #9 : Solving Separable Differential Equations And Using Them In Modeling
Solve the following separable differential equation with initial condition .
We proceed as follows
. Start
. Rewrite as .
. Multiply both sides by , and divide both sides by .
. Integrate both sides. Do not forget the on one of the sides.
Substitute the initial condition .
.
. Solve for .
. Exponentiate both sides .
. Rule of exponents.
Example Question #10 : Solving Separable Differential Equations And Using Them In Modeling
Solve the separable, first-order differential equation for :
Solve the separable, first-order differential equation for :
First collect all the terms with the derivative to one side of the equation.
Important Conceptual Note: often in texts on differential equations differentials often appear to have been rearranged algebraically as if is a "fraction," making it appear as if we "multiplied both sides" by to get: . This is not the case. The derivative is a limit by definition and, when the limit exists, can take on any real number which includes irrational numbers i.e. numbers which cannot be written as a ratio of two integers.
For instance, we cannot represent as a ratio, but some functions may have a derivative at a point such that the derivative is equal to , or a funciton may simply have an irrational number like as a derivative. For instance, if we write the derivative . Claiming that and are representative of a "numerator" and "denominator" respectively, we would essentially be claiming to have found a way to write an irrational number, such as as a ratio, which is preposterous. The expression is simply notation.
Here is what we are really doing.
Note that the constants of integration can just be combined into one constant by defining .
Solve for :
Applying the initial condition:
Here we have two possible solutions. However, because of the initial condition, we can easily rule out the negative solution. must be equal to positive .
Example Question #11 : Applications Of Antidifferentiation
Solve the separable differential equation
given the condition
None of the other answers
To solve this equation, we must separate the variables such that terms containing x and y are on the same side as dx and dy, respectively:
Integrating both sides of the equation, we get
The integrals were found using the following rules:
,
After combining the constants of integration into a single C, exponentiating both sides, and using the properties of exponents to simplify, we get
To solve for C, we use the condition given:
Our final answer is
Example Question #12 : Applications Of Antidifferentiation
is a function of . Solve for in this differential equation:
First, rewrite the expression on the right as the power of the radicand:
The expressions with can be separated from those with by multiplying both sides by :
Find the indefinite integral of both sides:
The expression on the right can be integrated using the Power Rule. On the right, use some -substitution, setting ; this makes and :
Apply some algebra to solve for :
Substitute back for , and apply some algebra:
Example Question #13 : Solving Separable Differential Equations And Using Them In Modeling
Solve the separable differential equation
where
To solve the separable differential equation, we must separate x and y to the same sides as their respective derivatives:
Next, we integrate both sides:
The integrals were solved using the following rules:
,
The two constants of integration were combined to make a single one.
Now, we exponentiate both sides to solve for y, keeping in mind rules for exponents which allow us to move the integration constant to the front:
To solve for the constant of integration, we use the condition given:
Our final answer is
Example Question #14 : Solving Separable Differential Equations And Using Them In Modeling
Solve the following separable differential equation:
given the condition that at
To solve the separable differential equation, we must separate x and y and their respective derivatives to either side of the equal sign:
Now, we integrate both sides of the equation:
The integrals were found using their identical rules.
Exponentiating both sides of the equation to solve for y - and keeping in mind the rules of exponents - we get
Now, we solve for the integration constant by using the condition given:
Our final answer is
Example Question #11 : Applications Of Antidifferentiation
Solve the following separable differential equation:
To solve the separable differential equation, we must separate x and y to the same sides as their respective derivatives:
Next, we integrate both sides, where on the lefthand side, the following substitution is made:
The integrals were solved using the following rules:
The two constants of integration were combined to make a single one.
Now, we solve for y:
Example Question #16 : Solving Separable Differential Equations And Using Them In Modeling
Solve the separable differential equation
given the initial condition
To solve the separable differential equation, we must separate x and y to the same sides as their respective derivatives:
Next, we integrate both sides:
The integrals were solved using the following rules:
,
The two constants of integration were combined to make a single constant.
Now, exponentiate both sides to isolate y, and use the properties of exponents to rearrange the integration constant:
(The exponential of the constant is another constant.)
Finally, we solve for the integration constant using the initial condition:
Our final answer is
Example Question #16 : Solving Separable Differential Equations And Using Them In Modeling
Solve the separable differential equation:
To solve the separable differential equation, we must separate x and y to the same sides as their respective derivatives:
Next, we integrate both sides:
The integrals were solved using the following rules:
,
The two constants of integration were combined to make a single one.
Now, we solve for y:
Because the problem statement said that y is negative - and y cannot be zero - our final answer is