Qu: Dear Math helpers, I have been tackling a book by Durell called School Algebra to improve my math skills and to improve my algebraic manipulation skills.
I have learn how to square trinomial such as (a+b+c)(a+b+c) etc. However, I have hit a bump.
I have shared the link of the book below and a picture of page. The place where i am stuck is page 283. The problem is that I don't understand the method and the example given by author.
The example was: Extact the square root of $x^4 - 6x^3 + 19x^2 - 30x + 25$
The book can be downloaded on the archive site (oso no copyrights issues) : https://archive.org/details/durellsschoolal01duregoog
Thank you ver much for your help