Let x<y be positive real numbers such that x+y=4 and x+2+y+2=5. Compute x.
A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.
Solution
Adding and subtracting both equations gives x+2+x+y+2+y=9x+2−x+y+2−y=1 Substitute a=x+x+2 and b=y+y+2. Then since (x+2+x)(x+2−x)=2, we have a+b=9a2+b2=1 Dividing the first equation by the second one gives ab=18,a=3,b=6 Lastly, x=2x+2+x−(x+2−x)=23−32=67, so x=3649.
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