Need help with factoring trinomials!?

Got a 10th-grader who's struggling with factoring trinomials in algebra. I'm trying to help him, I always was pretty good in algebra, but Richard Nixon was president when I took it in high school and Gerald Ford was president when I took it in college, so it's been a while (for those who are wondering, my wife and I became parents late in life). I've been able to connect with him on the little trick I remember where you have, for example, x^2+7x+44 and it factors out to (x+11)(x-4) with the little trick where the numbers you use to get the 44 (11 and -4) also give you the 7 when you find their sum. (I hope that makes sense.) However, I'm having trouble, and as such my son is having trouble, with problems such as 5L^2-26LX+5X^2. (Am using capital letters here so you'll know I'm using an L.) I know the answer, from a factoring calculator, is (5L-1X)(L-5X). And maybe I'm going about it the wrong way with the aforementioned trick about the sum and the product, but that doesn't work out with this equation and similar ones, and I'm having a devil of a time trying to show him how to get there and explain to him out to get there. Another similar problem (and these are from his work) is 20m^2+13mn+2n^2, I know the answer is (5m+2n)(4m+1n), but again am having diffculty showing him the concepts for getting there. His teacher at school has said he just cannot grasp the concepts despite repeated tries, I'm attempting to help him with it, and if there's anybody out there who can put me on the right track to helping him, I'd sure appreciate it. Thanks!