Last time, we looked at the standard algebraic methods to factor a quadratic trinomial. Those methods all involve some amount of guessing and checking, especially when the numbers involved are large; and they only work when there are binomial factors with integer coefficients. These are the methods a teacher usually expects you to use. But …
Last time, we looked at some non-recommended ways to factor a quadratic trinomial. Here we’ll explore several recommended methods (the basic case, trial-and-error, and ac-grouping), looking into how to do them, and why they work.
Recently in my college tutoring center, a student factored a quadratic polynomial using the X method, which I had heard of, but never watched being done for a hard example. Here on the site, a teacher recently asked about a related method I know as “slip-and-slide”. Both are “magical”, with no obvious reason they should …
Last time, we considered what the normal distribution and the z-score mean; here, we’ll look at some more recent questions demonstrating how to use them. In particular, we’ll see basic examples using a table, and then decide what to do when the right number isn’t there.
A recent question asked about quadratic inequalities; we’ve touched on that in Domain, Range, and Quadratic Inequalities, but here we’ll introduce three basic approaches. We’ll follow that with old questions about polynomial inequalities (mostly quadratic) and rational inequalities (fractions), expanding on the basic methods.
We’ve discussed the Rational Root Theorem in the past, but not a theorem that is often taught along with it, namely Descartes’ Rule of Signs, which predicts the numbers of positive and negative zeros (roots) of a polynomial. Both are ascribed to Rene Descartes; both are often taught without proof. Here we’ll introduce the theorem, …
A recent question reminded me that we haven’t yet covered completing the square, a technique important for solving quadratic equations, and also in several other applications. We’ll see the traditional method, and a modified method that avoids fractions, including a nice alternative to the quadratic formula.
In a discussion last April, we saw problems arising from integration by substitution, when the substitution is not one-to-one. Last time, I looked back at that issue from the perspective of a similar recent problem. But a question from soon after the first, with some interesting features of its own, led me to examine whether …
A question came in just this month, closely related to the last question in the post When Is an Improper Integral Not an Improper Integral? last April. There, we considered an integral where substitution led to a new integral with limits from 0 to 0, and after some discussion we decided that, while odd, the …
In searching for questions about polynomial division, I ran across several about problems where you are given the remainders when an unknown polynomial is divided by two or three different small polynomials, and have to find the remainder when it is divided by a different, but related, polynomial (typically the product of the others). We’ll …
Finding a Polynomial Remainder, Given Other Remainders Read More »