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 #1
avatar+130558 
+13

There is no answer to this......here's why....

The surface area is given by

Sa  = 480 =  2(lw + wh + lh)

240 = w( l + h) + lh

w = [240 - lh] / (l + h)

 

And the volume is given by

V = 2208 = lwh

2208/ [lh] = w

 

And setting the "w's"  equal, we have

2208/[lh] = [240- lh] / (l + h)    ..... cross-multiply

2208(l + h) = [240 - lh] lh

2208(l + h) = 240lh - (lh)^2     set to 0

(lh)^2 + 2208(l + h) - 240lh = 0

Now.....letting x = l and h = y.....look at the graph of

(xy)^2 + 2208(x + y) - 240xy = 0

https://www.desmos.com/calculator/eocxww2vmh

Notice that l and h both have to be greater than 0 because they are both lengths. Thus, x and y have to be greater than 0.

But notice.......if x and y were greater than 0, at least part of the graph would have to exist in the first quadrant....but it doesn't

Thus, there are no solutions......

 

P.S.  .....would another mathematician check my logic here???......I believe this is correct, but I'm not sure.....!!!!

  

17 мар. 2015 г.