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eroshea
Group Title
Find the number of sides of each of the two polygons if the total number of sides of the polygons is 13, and the sum of the number of diagonals of the polygons is 25.
 2 years ago
 2 years ago
eroshea Group Title
Find the number of sides of each of the two polygons if the total number of sides of the polygons is 13, and the sum of the number of diagonals of the polygons is 25.
 2 years ago
 2 years ago

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hartnn Group TitleBest ResponseYou've already chosen the best response.1
polygon of n sides have how many diagonals ?
 2 years ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
[n(n3)]/2 ... is that it?
 2 years ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
yes, so u could u form 2 equations using this formula?
 2 years ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
take side of one polygon as x and other as y x+y=13 [x(x3)]/2+[y(y3)]/2 = 25
 2 years ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
after that?
 2 years ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
can u work out second equation and tell me what u get as x^2+y^2= ?
 2 years ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
got it :)) the two polygon has 5 and 8 sides
 2 years ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
yes! that is correct. u had options ?
 2 years ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
i guess none... im just finding the sides of the two polygons is there a possible option for this problem? if there is, can you tell me what it may be?
 2 years ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
by option , i meant choices.
 2 years ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
owh.. hahaha! my bad.. none :)
 2 years ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
then u worked it out to get 5, 8 ? nice!
 2 years ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
yes! :)) you helped me a lot there..
 2 years ago

pjaesecarilla Group TitleBest ResponseYou've already chosen the best response.0
hello there :) can i ask @hartnn what you meant by "can u work out second equation and tell me what u get as x^2+y^2= ?" sorry i also encountered this problem on my solid mensuration
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
so, did u get how i got this : [x(x3)]/2+[y(y3)]/2 = 25 ?
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
when sides is 'x' number of diagonals is x (x3)/2 same for y and total number of diagonals = 25
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
that can be simplified as \([x(x3)]/2+[y(y3)]/2 = 25 \\ x^23x+y^23y=50 \\ (x^2+y^2)3(x+y)=50\) but we know x+y =13 so, \(x^2+y^23\times 13=50\) we can easily find x^2+y^2 from here.
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
and once we know x^2+y^2 and x+y , we can find x and y you know how to ? or need help with that ?
 one year ago

pjaesecarilla Group TitleBest ResponseYou've already chosen the best response.0
uhhhh help please :)
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
ok, so we use the fact that (x+y)^2 = x^2+y^2 +2xy from this we will get xy. right ? then (xy)^2 = x^2+y^2 2xy from this we will get xy , ok ? and now we have xy, x+y if we just add then, 'y' gets eliminated and you get the value of x try once, if you get stuck, i will show you the entire solution
 one year ago

pjaesecarilla Group TitleBest ResponseYou've already chosen the best response.0
ummm is xy=40?
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
yes ! it is :) xy =40 is correct. what u got for xy ?
 one year ago

pjaesecarilla Group TitleBest ResponseYou've already chosen the best response.0
i kinda got stuck on that one. (xy)^2 = x^2+y^22xy x^2=89y^2 so. 89y^2 + y^2  2(40) so i got 9. i dunno if im correct :/
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
see, (xy)^2 = x^2+y^2 2xy = 89 2(40) = 9 so, xy = 3
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
x+y = 13 xy =3 just add them
 one year ago

pjaesecarilla Group TitleBest ResponseYou've already chosen the best response.0
OOOOOOOOOOOOHHHHHHHHH!!!!!!! ok thanks man VERY MUCH haha i get it now :))))
 one year ago

imehs18 Group TitleBest ResponseYou've already chosen the best response.0
hi pjaesecarilla and hartnn would like to ask about this question. im having problem as well.. how did you get the xy=40
 one year ago

imehs18 Group TitleBest ResponseYou've already chosen the best response.0
hi @pjaesecarilla and @hartnn would like to ask about this question. im having problem as well.. how did you get the xy=40
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.1
x+y = 13 x^2+y^2 39 = 50 , so x^2+y^2 = 50+39 = 89 (x+y)^2 = x^2+2xy +y^2 13^2 = 89 + 2xy 169 = 89 +2xy 2xy =16989 = 80 xy =40 :)
 one year ago

stephengmt Group TitleBest ResponseYou've already chosen the best response.0
where did the xy come from? :) pls help thaaaaaaaaanks
 4 months ago
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