SOLUTION: Can some one please help explain these in detail? I am so lost. Thank you Factor completely: 9x^2 -16y^2 3x^2-2x-8 3x^2 + 12x +12 Thanks again for all your help!

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Can some one please help explain these in detail? I am so lost. Thank you Factor completely: 9x^2 -16y^2 3x^2-2x-8 3x^2 + 12x +12 Thanks again for all your help!       Log On


   



Question 35705: Can some one please help explain these in detail? I am so lost. Thank you
Factor completely:
9x^2 -16y^2
3x^2-2x-8
3x^2 + 12x +12
Thanks again for all your help!



Thank you

Found 2 solutions by rapaljer, Earlsdon:
Answer by rapaljer(4671) About Me  (Show Source):
You can put this solution on YOUR website!
From the variety of factoring problems you have here, you probably need to visit my website by clicking on my user name "rapaljer" anywhere in algebra.com. Then go to Basic Algebra, and look for "Samples from Basic Algebra: One Step at a Time". Click on Chapter 2, and see all the sections on factoring. This contains all the explanation, examples, exercises, and answers and it's all FREE. Check it out. Many if not all of these are also Lesson Plans on algebra.com if you want to look for them here.

Now, 9x%5E2+-+16y%5E2 is a difference of squares.
+%283x-4y%29%283x%2B4y%29+

Secondly, 3x%5E2-2x-8 comes from a section that I call "Advanced Trinomial Factoring". This is a hard one for most people. You have to start off with a 3x%5E2 which can only be factored into 3x*x.
+%283x+____%29%2A%28x______%29+
The last times last must come out to a -8, so I would try a 4 times 2 or a 2 times 4 combination. By trial and error (see my website for details!), it turns out that the 4 should come first and the 2 should go second like this:
+%283x++%2B+4%29%2A%28x++-++2%29+
The outer times outer is -6x and the inner times inner is 4x for a total of -2x, which checks for the middle term.

3x%5E2+%2B+12x+%2B12 is a problem that turns out to be a perfect square trinomial (in my website, this is in with the difference of squares section).
You must first take out the common factor which is 3:
3%28x%5E2%2B+4x%2B4%29
Next, factor the trinomial:
3%28x%2B2%29%28x%2B2%29+=+3%28x%2B2%29%5E2

R^2 at SCC


Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Factor:
1) 9x%5E2+-+16y%5E2 This is the difference of two squares and can be factored as follows:
A%5E2+-+B%5E2+=+%28A%2BB%29%28A-B%29 Applying this to your problem:
9x%5E2+-+16y%5E2+=+%283x%29%5E2+-+%284y%29%5E2 = %283x%2B4y%29%283x-4y%29
2) 3x%5E2+-+2x+-+8
The factors of 3x^2 are:(3x)(x)
The factors of -8 are: (-1)(8) or (-2)(4) or (2)(-4)
Try %283x%2B4%29%28x-2%29+=+3x%5E2-6x%2B4x-8= 3x%5E2-2x-8
The factors are: %283x%2B4%29%28x-2%29
3) 3x%5E2%2B12x%2B12
The factors of 3x are:(3x)(x)
The factor of 12 are: (1)(12) or (2)(6) or (3)(4)
Try %283x%2B6%29%28x%2B2%29+=+3x%5E2%2B6x%2B6x%2B12=3x%5E2%2B12x%2B12
The factors are: %283x%2B6%29%28x%2B2%29