+5 Solution: x+y=xy/18 - find x, y where x, y ∈ ℤ+ using Simon's Favorite Factoring Tricks
18(x+y)=(xy)18/18
18x+18y=xy
18x+18y-xy=0
18x+y(18-x)=0
y(18-x)+18x=0
y(x-18)-18x=0
y(x-18)-18x+324=324 ⇒ 18*18=324
y(x-18)-18(x-18)=324
(x-18)(y-18)=(27)(12) ⇒ 27*12=324
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x-18=27 => x=45
y-18=12 => y=30
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x+y=xy/18
45+30=45*30/18
75=75
