Loser66
  • Loser66
A total x feet of fencing is to form 3 sides of a level rectangular yard. What is the maximum area of the yard in term of x? A) x^2/9 B) x^2/8 C) x^2/4 D)x^2 E)2x^2 Please, help
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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chestercat
  • chestercat
I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!
freckles
  • freckles
oops meant to write x
freckles
  • freckles
one sec
freckles
  • freckles
\[2L+W=x \\ A=LW=L(x-2L)\]

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freckles
  • freckles
So we want to find A' here
Loser66
  • Loser66
yes, then??
freckles
  • freckles
x is a constant I believe \[A=Lx-2L^2 \\ A'=x-4L \\ A'=0 \implies x=4L \\ A=L(x-2L)=L(4L-2L)=L(2L)=2L^2 \\ \] I think you can find A in terms of x now since x=4L
freckles
  • freckles
still processing?
Loser66
  • Loser66
Yes. Thanks a lot. I got the right answer. It is not test, just practice exam with the answer sheet. But I want to know logic.
freckles
  • freckles
Why are you doing calculus 1 problems?
Loser66
  • Loser66
oh, is it calculus problem??
freckles
  • freckles
Yes it is an optimization problem
Loser66
  • Loser66
Question: why do you link to derivative?
freckles
  • freckles
because it say to maximize
Loser66
  • Loser66
I assume it is an algebra problem and get no outlet
freckles
  • freckles
usually those in the cal problems I have seen they actually gave a number instead of saying x
Loser66
  • Loser66
I am prepare for my GRE test for maths major students. ha!!!
freckles
  • freckles
http://tutorial.math.lamar.edu/Classes/CalcI/Optimization.aspx this example one here is pretty similar
Loser66
  • Loser66
My tough one is English, not math.
freckles
  • freckles
except as I said they say 500 feet instead of x feet
Loser66
  • Loser66
Any tips for GRE math practice?? I have only 1. :)
freckles
  • freckles
there was a question and I think it was on the gre it was my favorite question to give me a sec and I will remember it
freckles
  • freckles
solve for x+y \[x^2+y^2+2xy+2x+2y=-1 \]
freckles
  • freckles
there was a similar question on the gre or it might have been on another standard test can't remember which standard test
Loser66
  • Loser66
hihihi... I have time. I will study carefully before taking the test. But you know, I am old. hahaha..... I am slow!!
freckles
  • freckles
that question isn't too bad did you want me to show you how to do it or did you want to try it first
Loser66
  • Loser66
show me, please
freckles
  • freckles
\[x^2+2xy+y^2+2x+2y+1=0 \\ (x+y)^2+2(x+y)+1=0 \\ (x+y+1)^2=0 \\ x+y+1=0 \\ x+y=-1 \]
freckles
  • freckles
I turned it into a quadratic in terms of (x+y)
Loser66
  • Loser66
What if we let x+y =t??
Loser66
  • Loser66
oh, yea, we met there
freckles
  • freckles
good luck on your gre if i could figure out anything to tell you to help you I will I probably should have studied for it back in the day more than I did
Loser66
  • Loser66
Sure. Again, thanks for the help.
freckles
  • freckles
np
Loser66
  • Loser66
What is the units digit in standard decimal expansion of the number 7^(25) I don't get what it mean
Loser66
  • Loser66
since \(7^{25} = 1.34106862 *10^{21}\) hence the number of digits after decimal point is 8 but it is not one of the options which are 1,3,5,7 or 9
Loser66
  • Loser66
@freckles
Loser66
  • Loser66
To this problem, if I don't have calculator, how can I find out the answer?
freckles
  • freckles
so you are trying to find out the length of the number 7^(25) ?
Loser66
  • Loser66
problem 14 https://www.ets.org/s/gre/pdf/practice_book_math.pdf
freckles
  • freckles
on
freckles
  • freckles
oh*
freckles
  • freckles
the units digit is the ones digit
freckles
  • freckles
answer is 1
Loser66
  • Loser66
total??
Loser66
  • Loser66
nope, answer is 7
freckles
  • freckles
wait standard notation is not scientific notation is it ?
Loser66
  • Loser66
I am not sure.
freckles
  • freckles
there was need to write in scientific notation because standard notation is different from scientific notation
freckles
  • freckles
7^(25) mod 10 will give you number in 1's digit
freckles
  • freckles
or aka units digit
freckles
  • freckles
\[4^2=16 \text{; 16 is standard notation for } 4^2 \\ 4^2=1.6 \times 10 \text{ is sceinfict notation }\]
freckles
  • freckles
I missed the word no in there was need to write in scientific notation there was no need to write in scientific notation*
Loser66
  • Loser66
to this http://mathcentral.uregina.ca/QQ/database/QQ.09.06/tyrone1.html they said that the units digit is the last digit of the number in standard form in decimal form, the unit digit of 7^25 is the last one, which is 2, not 7 : (
freckles
  • freckles
\[7^{2} \mod 10=9 \\ 7^4 \mod 10 =9 \cdot 9 \mod 10=81 \mod 10=1 \\ 7^{4(6)+1} \mod 10=(7^4)^6(7) \mod 10=1^6(7) \mod 10 =7 \\ 7^{25} \mod 10=7 \]
freckles
  • freckles
the units digit is the first number it is the one's digit that is what that picture above says also
freckles
  • freckles
for example 61 do you call 1 the first digit because I do and 6 is the last digit 1 is in the one's place (or the units place) 6 is in the ten's palce
freckles
  • freckles
oh I think I see where you are getting confused
freckles
  • freckles
\[7^{25} = 1.34106862 *10^{21} \] you think this equality is exact when it is not
freckles
  • freckles
and even if it was exact you would say the units digit is 0 but it is not the case because this equation is not exact
freckles
  • freckles
like you still need to move that decimal to the right like 21 times
freckles
  • freckles
2 is not in the one's digit
freckles
  • freckles
http://www.wolframalpha.com/input/?i=7%5E25+
freckles
  • freckles
the number where it says result is the number in standard notation
Loser66
  • Loser66
oooooooooooooooooh!! got you
freckles
  • freckles
a mod 10 should always give you the units digit of a
Loser66
  • Loser66
modular method help me out 7^0 -----1 last digit 7^1 -----7 last digit 7^2 -----9 7^3 -----3 7^4-----1 hence the cycle is 4, 25 = 4*6 +1, hence \(7^25 = 7^24 *7 , but the last digit of 7^24 is 1 then *7 =7
freckles
  • freckles
yah
Loser66
  • Loser66
Thanks a ton. :) I do appreciate.
freckles
  • freckles
np
freckles
  • freckles
interesting practice exam I think they have made changes to it seen I last took the gre I feel like that was 8 years ago or something :p
freckles
  • freckles
I don't remember linear algebra or number theory on it
freckles
  • freckles
but maybe there was some

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