Will you guys help me with my algebra homework today?
This one problem is just kicking my butt. It’s an on-line course, and when I ask the instructor for help, whenever she gets around to replying she sends back a message that’s basically a duplicate of what I get when I click the help tab on the lesson. I have to have this last unit done today, as well as a chapter test. It’s all due tomorrow morning at 8:00 a.m.
Here is the problem:
x – (1.8x – 4(x-3.1(x+11)))=0 (don’t fuss over the parenthesis signs..)
I get this far
x – (1.8 – 4(x – 3.1x – 34.1))=0
x – (1.8 – 4x – 45.7x + 136.4)=0
x – (1.8x) – (4x) – (12.4x) – (136.4)
Following is where I get confused because the signs change at random, or so it seems to me. I just need some sort of trick to memorize that will allow me to start flipping signs around as needed. The example shows that the next step is:
x-1.8x + 4x - 12.4x – 136.4 = 0.
Please explain how x – (- 4x) turns into + 4x, whereas x- (-12.4x) says with the – sign…....
Also, to me, the explanations get all long a drawn out and there always seems to be one step that is a little redundant. In this case I think I can get by without the “x – (1.8x) – (4x) – (12.4x) – (136.4)” step….if I can puzzle out why the signs change.
I have such a headache.
Lol! I went to preview the question and every thing was crossed out ! :)
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12 Answers
I’ll give you a hint:
Your problem is here:
x – (1.8 – 4(x – 3.1x – 34.1))=0
x – (1.8 – 4x – 45.7x + 136.4)=0
Where does the -45.7x come from? Should it really be negative?
Help me break it down one step at a time.
x – 1.8 = -1.8x.
– 1.8x – 4x = – 5.8x.
– 5.8x – 45.7 x = -51.5… OK, I’m stumped. Why wouldn’t t be – 45x. I can use more than hints. I need education. I’m not simply looking for The Answer. I want to understand. I’m taking this class for two reasons, one of which is I have to teach algebra at the High School level. Can’t teach something you can’t master yourself.
Thanks @roundsquare
Does this help?
x – (1.8x – 4(x-3.1(x+11)))=0
x – (1.8x – 4(x – 3.1x – 34.1)) = 0
x – (1.8x – 4x + 12.4x + 136.4) = 0 <—- See here how 12.4x is positive.
Ok..yes, I do see it now…. a negative times a negative is a positive.
So,next I have
-2.2x+12.4x + 136.4
10.2x + 136.4 = 0
.....if these numbers are right, the rest is a piece of cake…and I’ve come up with this answer before but I just don’t think it’s right….
just got through this with my daughter in her math course.
the negative sign before a parentheses is distributed over all the terms inside the parentheses, so each term inside the parentheses gets flipped (negated) once you remove the parentheses.
K….I think I’m closing in….
No, I’m not. I went wrong somewhere in here:
-1.2x+13.6x+364.4=0
12.4x+364.4=0
Starting where @roundsquare left off:
x = (1.8x – 4x + 12.4x + 136.4)
x = ((1.8 – 4 + 12.4)x + 136.4)
x = (((1.8 – 4) + 12.4)x + 136.4)
x = ((-2.2 + 12.4)x + 136.4)
x = 10.2x + 136.4
@ratboy Thank you. That was the last problem in a section, and I have one more section, about 22 questions, to do. So I set that last one aside for now. I’ll get back to it when I finish this last section. Thank you. TTU soon…..
Treating the minus sign as a factor ’-1’ in a multiplication might help, so -x is the same as -1 times x. When x is the sum of say a + b +c you can also write -1 times a + -1 times b + -1 times c.
@Dutchess_III – I find it totally awesome that you are learning algebra. Yotta zetta mega cool !
@mattbrowne Heh! I’m RE learning it dude! I’ve taken it before, but it was a long time ago. I’m on plotting slopes now. It’s SOOOOOOO easy IF you ignore all their directions and explanations and figure out what it is you need to do, and come up with your own formula for remembering it. I don’t know why they have to make it so complicated.
@Dutchess_III Its because they don’t think people can learn concepts so they need to give directions. Its sad, math books teach math in exactly the wrong way.
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