Limit and Continuity Find the limit (if it exists) and discuss the continuity of

Find the local maximum and minimum values and saddle points of the function. If you have three-dimensional graphing software, graph the function with a domain and viewpoint that reveal all the important aspects of the function
$f(x,y)=x^3-6xy+8y^3$

$\frac{1}{\sec <!--\; \; -->(x)}$ in derivative?

What is the derivative of ${\displaystyle \ln (x+1)}$?

What is the limit of ${\displaystyle e^{-x}}$ as ${\displaystyle x\to \infty }$?

What is the derivative of ${\displaystyle f\left(x\right)=5^{\ln x}}$?

What is the derivative of ${\displaystyle e^{-2x}}$?

How to find ${\displaystyle lim\frac{e^t-1}{t}}$ as ${\displaystyle t\to 0}$ using l'Hospital's Rule?

What is the integral of ${\displaystyle \sqrt{9-x^2}}$?

What is the derivative of ${\displaystyle f\left(x\right)=\ln \left[x^9{(x+3)}^6{(x^2+7)}^5\right]}$ ?

What Is the common difference or common ratio of the sequence 2, 5, 8, 11...?

How to find the derivative of ${\displaystyle y=e^{5x}}$?

How to evaluate the limit ${\displaystyle \frac{\sin \left(5x\right)}{x}}$ as x approaches 0?

How to find derivatives of parametric functions?

What is the antiderivative of ${\displaystyle -5e^{x-1}}$?

How to evaluate: indefinite integral ${\displaystyle \frac{1+x}{1+x^2}dx}$?