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eroshea
 2 years ago
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.
eroshea
 2 years ago
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.

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

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

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

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

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

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

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

eroshea
 2 years ago
Best ResponseYou've already chosen the best response.1i 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?

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

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

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

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

pjaesecarilla
 one year ago
Best ResponseYou've already chosen the best response.0hello 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

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

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

hartnn
 one year ago
Best ResponseYou've already chosen the best response.1that 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.

hartnn
 one year ago
Best ResponseYou've already chosen the best response.1and 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 ?

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

hartnn
 one year ago
Best ResponseYou've already chosen the best response.1ok, 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

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

pjaesecarilla
 one year ago
Best ResponseYou've already chosen the best response.0i 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 :/

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

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

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

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

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

hartnn
 one year ago
Best ResponseYou've already chosen the best response.1x+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 :)

stephengmt
 one year ago
Best ResponseYou've already chosen the best response.0where did the xy come from? :) pls help thaaaaaaaaanks
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