Find the value of each variable. If an answer isn't a whole number, then leave it in simplest radical form. Picture will be drawn and medal will be rewarded. Please explain & show work to get the medal, so I understand how you got the answer you got.

Question

firejay5 · Answer

|dw:1391474777947:dw|

firejay5 · Answer

@jim_thompson5910

nikato · Answer

I forgot the reason but I think the sides would be proportional
So

21/ (21+2.1x ) = x/ (x+40)
And solve for x. U can start by cross multiplying

firejay5 · Answer

@nikato  can you show me what the result would be when it's cross multiplied

nikato · Answer

Sure.

21(x+40)= x(21+2.1x)
21x+ 840= 21x+ 2.1x^2
-21x-840.  -21x-840
--------------------------
2.1x^2 -840=0

nikato · Answer

Then factor out a 2.1
So
2.1(x^2 -400)=0
Factor again
2.1(x-20)(x+20)=0
So x=20 or -20

firejay5 · Answer

how would you get 20 or -20

nikato · Answer

Because u can just ignore the 2.1
U have (x-20)(x+20)=0
So
x-20=0. Or x+20=0
So x=20 or x=-20