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2014-04-24T16:25:49+03:00
13^2-x^2=15^2-(14-x)^2
169-x^2=225-(196-28x+x^2)
169-x^2=225-196+28x-x^2   -x^2 se reduce
169-225+196=28x
140=28x
x=140:28
x=5
2 5 2