I’m supposed to draw a graph for this function
f(a)=w(18-w)
i have no clue how to do it, a stands for area w stands for width and 18 is the lenth
its for a problem regarding fencing
If we tell you how to do it, you’ll come through this still having no clue.
This is why you’re in school… to learn how to do such things.
I suggest you start with what you know (can you graph y = x^2 ?) then see how this equation is different from the equation you’ve given us. Have you found the form of your equation that has a w^2 term? Perhaps this might be your first step.
Perhaps make a table… one column with values of x, one with values of y, and one with values of f(x). See how the y and f(x) columns vary.
Use the table to plot your graph. For each row, make a dot on the graph. Connect the dots.
i barely understood any of this, i’m not stupid i just am very bad at algebra. i don’t understand what you’re saying in the y=x^2. I already have a table but its values for length width and area.
i figured if i started from the beginning you might be able to hint me in the right direction without actually telling me.
i have a table basically like this
Width Length Area
1 17 17
2 16 32
3 15 45
4 14 56
the first part of the project is this
(a) Looking through your table you should see a relationship between the length and the width of the rectangle. What type of function could represent this relationship? Write and equation giving the length as a function of the width.
for this my answer was f(L)=18-w
is that a correct answer
You should probably be using a foil for fencing. Equations are useless when it comes to armed combat.
You’ve got all the tools you need to find out for yourself.
Take your equation and “test” it against each row in the table. If the equation holds for every row, then it should be good. If you’ve still any doubt, make the table bigger and do some more tests.
If you’ve still any doubt after that, you’d need to use induction to test your equation, but that’s a higher level of math than it seems you’re expected to know right now.
Go with your gut feeling. If it feels good, push ahead.
first off, f(a) is misleading, it should be f(L,w) but L is a function of w so it REALLY should read f(w) . . . but I digress
find the zeros============= f(a) = 0 when: w = 0 and w = 18 : ) makes sense right? if either term w or (18-w) is = 0 then the whole thing is.
you also know it’s a quadratic, and that it’s dominant term is negative, so you know it will be like an “n” shape, not “u”
for a simple quadratic, just take the midpoint of the 2 zeros and plug it in (in this case 9) so you get 9*9 = 81 which is the peak of your curve at w = 9
. . . . I hope that helps. . . .
yes, 18-w is the length, and w is the width, thus this graph is a function of area from 1 to 4 only, you don’t have any other info.
The graph of f(a)=w(18-w) is just a horizontal line, because w is constant.
As for f(w)=w(18-w), well…
The derivative is -2w+18, so the maximum is at f(9)=89
From there, it’s just like the graph of -w^2.
It’s two step graphing that involves a single calculation.
EDIT: Let me guess: Is f(w) the area and w the width of the fenced space?
Don’t contradict yourself;)
Maestro8 told you to make a table and plot points. If you can’t do this, you shouldn’t have passed algebra 1.
If you can’t use the method I described, don’t worry. You won’t encounter it until differential calculus (probably).
The main thing is to not over-complicate things. Math is just simple logic applied to a finite number of key concepts.
well don’t tell anyone but i didn’t actually take alg 1
buttttt, i do infact know how to do that, and i have progressed further with the problem. it was simply a question of graphing it.
i need to study functions alot more, as a whole they kind of confuse me and i think if i understood them better i wouldn’t be having so much trouble.
Well, for starters, f(x)=x is a function of x…
f(a)=x is a function of a.
For example,
f(a)=xa can be represented by a line of slope x, passing through the origin. x is a constant.
f(L)=18-w is a function of L. w is constant, unless you define it as a variable in terms of L(maybe for a substitution?)
Say, w=2L, then
f(L)=18-w=18-2L
I think you meant that L, or length, is equal to f(w)=18-w
It’s OK to simply say that L=18-w, or that A=w(18-w)
This may not seem important now, but if you don’t fix it, then it will confuse you greatly in the future.
Algebra consists of equations, functions, and expressions. Yeah, one could say that functions are kind of fundamental.
i spent a bunch of time going over functions last night
i’m starting to understand it more
its just the whole idea of graphing them the confuses me
but i’m closer
Whoa you live? Do you still ride atall?
lol, hobo chuck, 
read my post up top, you restated everything xP
btw, that derivative was right, and f(9) = 81, not 89 : P silly goose
hey when are we getting into differential equations, because I can rock some socks off at that too : )
::insert ramblin’ wreck fight song here::
yeah man, don’t ride so much anymore i was riding around the other day. not doing crazy stuff anymore i was doing some hicks yesterday
yeahhh i ended up figuring out the graphing aspect so i’m all set
Typo.
9^2
Durrrr slaps chest with limp hand
It’s really stupid, though.
It needs fewer "btw"s and "============= "s and more capitalized letters and punctuation.
Also, the 
emote on these forums uses the lowercase p.
Finally, what the hell is this?
I’m an engineer, not an english major : P I like my silly face fine, and my explaination is not stupid at all. If it’s understandable, then it serves its purpose.
he gave a chart, it had 4 plot points on it. They want a trend line, but unless it’s stated, you can only assume that is the trend between the outter most points, which are w =1 and w = 4 obviously width cannot be a negative number, nor will it go off into infinity.
now what’s with the attitude? I don’t recall killing and puppies recently. . .
I don’t get onto forums to be harrassed about my grammar and not making emotes correctly. It kinda makes me sick that you would bring up all of that.
…wait a minute… why am I apologizing?
Five minutes in Excel/Numbers and you’re done. No comprehension required.
