Delta equals zero in rational indefinite integrals

Factoring a Quadratic Trinomial

In rational indefinite integrals, we often need to factor a quadratic trinomial: . We do this of course using the formula: , which works when increment greater than 0.

Rational Integrals and Delta Equals 0


But how does this binomial look when Delta is precisely 0? For instance, how does this factor look: ?

Is it like this:  ?

Of course not… From high school, we remember that if then we get one root, but it’s a double root. So in our example, we can say: , meaning the quadratic trinomial factored looks like this:

This has significant consequences for rational indefinite integrals when breaking them into simple fractions.

Example

Let’s take an example:

We break down the fraction by itself without the integral, writing:

We factor out an x in the denominator:

From the quadratic trinomial in the denominator, we compute the delta, which is 0, and get a root of (-1). Factoring it, we get:

And breaking it down into simple fractions:

Krystian Karczyński

Założyciel i szef serwisu eTrapez.

Magister matematyki Politechniki Poznańskiej. Korepetytor matematyki z wieloletnim stażem. Twórca pierwszych Kursów eTrapez, które zdobyły ogromną popularność wśród studentów w całej Polsce.

Mieszka w Szczecinie. Lubi spacery po lesie, plażowanie i kajaki.

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