Here's the question you clicked on:
kdarnell08
4x^2+81-36x
can ya go through the steps for me?
There are a couple of ways to do this. The quickest is factoring, if you are good at seeing factors. This is a little tricky with factoring, so when in doubt you can always use the quadratic formula (the second way) which is actually my favorite way.\[x = \frac{ -b \pm \sqrt{b ^{2} - 4ac} }{ 2a }\]where you have an equation in the form: ax^2 + bx + c = 0 So you have a=4, b=-36, and c=81 So, you substitute those into the formula.
ughh i just dont understand this!!
Well, let's look at factoring for a bit instead. As for factoring (the other way), you can rewrite the equation into: (2x)^2 - 36x + 9^2 You will see that the first term is a square and the third term is a square which might sugeest that the factors are squared.
That means that we can partially set up the solution: (2x )(2x ) But the third term is a square also, so going a bit further and just leaving out the signs: (2x 9)(2x 9) Now this all presupposes you can work the distributive law well enough: (a + b)(c + d) = a(c + d) + b(c + d) = ac + ad + bc + bd Tell me before we go any further, can you deal with that last equation?
That's great! That really is. Don't worry if it's a little rocky. You're not supposed to "see it all" right away, so we'll just go along until it gets murky for you. np. So, continuing where we left off with the factoring, writing it again: (2x 9)(2x 9) We have a good start, but we don't have signs yet. We know that 81 is positive so the signs are both negative or both positive. Since the 36x has a negative sign, we go with negative signs: (2x - 9)(2x - 9)
Now, we are goingto multiply this out to check our work: (2x)(2x - 9) - 9(2x - 9) = 4x^2 - 18x - 18x + 81 = 4x^2 - 36x + 81
So, that's the same as our original expression with a slight change in order of the terms. So, that's 2 ways to do this. Ok, your turn, ask questions.
ok. i understand most of it i just dont understand what happened to the #36
In the checking of the solution that I did, the -36x came from the -18x -18x
Believe me. If really get this or most of it, or even half. That's real progress! For anyone! I suggest going over this a couple times to consolidate your understanding
And don't give up on the quadratic formula because that is actually much more important.
ok i already copied and pasted it to a word document. and ive used the equations for more than one of the other problems i have!
You very nice to work with because you really want to learn (all students should be that way) and you are a nice person.
thank you! i appreciate that. maybe its because they are mostly in high school. im in nursing school and am relearning everything and harly remember it all. i personallt DO NOT want to have to repay for this class. hs was 5 years ago so its a little more than rocky.
and its an online class. which is way harder than on campus
This is good what you just said. You are approaching this from a perspective that is more mature than high school. And the world needs good nurses. My sister is a nurse. She was also a math whiz, so she breezed through math. But just get through math since you already have a higher goal. And good luck in both math but especially the nursing!
You are entirely welcome!
did i mention i hate rational expressions :)
lol then go with the irrational ones :-)
A little math humor. There's so little material from which to get humor in math!
haha. oh i am aware!
I think the developers of all these math formulas are secretly laughing in their graves at all the misery they caused!
I know! Maybe one day you can get a math PhD. as a patient! Payback!
hahahahaha. thats funny!!! i wouldnt doubt it!! all i know is this is the only subject that i curl up in the fetal position and cry over ;)
Math is tough because it is so unforgiving and as a field of study, it is so vertical. Can't go too far ahead without getting the basics.
uh oh. got to another one....wanna help?
vertical as in concepts building upon one another. Sure, I've got time for one more. Then I curl up and cry.
\[\frac{ x ^{2}-25 }{ x+5 }\]
Oh, you'll like this one because it's easier than the other one.
oh god i hope so lol
dont you get rid of the division and turn it to multipication
Sort of. I'm going to factor the numerator:\[\frac{ (x + 5) \times (x - 5) }{ (x + 5) }\]Now, the division concept comes into play insofar as the x + 5 factor cancels out of the numerator and the denominator and you are left with: x - 5 as your answer.
that i comletely understand!
Either the website or my computer just went goofy.