# Archives

Author Archive for: ‘roberts@protutorcompany.com’

## Now Tutoring in Northern Delaware

Hey folks, Keith Roberts here. I’m happy to announce that I am now adding in-person tutoring to my service list in northern Delaware. I’ll be primarily reaching out to the New Castle, Wilmington, Newark, Bear, and Hockessin areas, but I may be able to come out to your area if it’s not one of these. Here is how it works: …

## How Do I Find the Focus of a Parabola?

This is a common question that we get from two audiences. It is most commonly asked by algebra students who want to calculate the point in the plane, when the equation of the parabola is given. More advanced students sometimes must prove this formula from the definition of the focus. We will handle this scenario second. We have also included …

## How Do I Know Which Direction the Parabola Opens?

From the Value of a There are a couple of ways we can determine the direction the parabola opens. The a-value is one way. If a > 0, then the parabola opens upward. If a < 0, then the parabola opens downward. Recall that when the parabola is given in standard form, y = ax² + bx + c, the …

## Finding the Directrix of a Parabola, Given its Vertex and Focus    Determining the Orientation of the Parabola Any time we are given only one or more of the following: Focus Vertex Axis of Symmetry Directrix and are asked to find one or more of the others, we must first determine the orientation of the parabola, if we are not already told what it is (as we usually are not). In the …

## Finding the Vertex, Focus, and Directrix of a Parabola Given in Standard Form    Watch two things in these types of problems. First, the geometry of the situation — i.e. the orientation of the parabola and its various parts; and second, make sure your formulas are properly applied, as there are many k’s, p’s and a’s floating around and are a lot to contend with. SEE ALSO: How to find the directrix of a …

## Algebra Word Problem – Accounting Application    Problem – Algebra – Accounting Applications In this problem, we walk through a word problem involving an accounting application in which we must calculate changes in owner’s equity based on information given about its assets and liabilities and their changes over the year. These problems can be tricky. The thing to keep in mind is that balance sheets reflect the …

## Multiplying and Dividing Fractions    Problem – Basic Math/Algebra – Multiplication and Division of Fractions This is a video session on how to multiply and divide fractions, as how students generally encounter it in Pre-Algebra and early Algebra courses. Notice that the illustration starts off with some relatively simple multiplication problems, and ultimately ends with some more complex division of mixed numbers. This wasn’t an …

## Calculating Compound Interest    Problem – Pre-Calculus – How to Calculate Compound Interest on an Investment In this problem, we walk through a question on calculating compound interest. In the explanation video, we spend some time on on the compound interest formula, itself, and distinguish it from simple interest scenarios. Comparison with Simple Interest: Notice that at the end of the investment period, you …