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 #3
avatar+137 
+1
Jul 12, 2021
 #1
avatar+26396 
+2

Find all pairs (x,y) of real numbers such that
x+y=10x2+y2=56+xy.

 

a+b=10b=10a

 

(x+y)2=x2+2xy+y2(x+y)2=x2+y2+2xy|x2+y2=56+xy102=56+xy+2xy102=56+3xy3xy=100563xy=44|:3xy=443|y=10xx(10x)=44310xx2=443x210x+443=0x=10±10244432x=10±42544432x=10±2254432x=5±25443x=5±75443x=5±313

 

1.

x=5+313y=10a=10(5+313)y=5313

 

2.

x=5313y=10a=10(5313)y=5+313

 

laugh

Jul 12, 2021
 #1
avatar+26396 
+2

Find all solutions to the system
a+b=14a3+b3=812+3ab

 

a+b=14b=14a

 

(a+b)3=a3+3a2b+3ab2+b3(a+b)3=a3+b3+3ab(a+b)|a+b=14143=a3+b3+314ab|a3+b3=812+3ab143=812+3ab+314ab143=812+315ab315ab=143812315ab=1932|:315ab=644|b=14a15a(14a)=644a(14a)=6441514aa2=64415a214a+64415=0a=14±1424644152a=14±4494644152a=14±249644152a=7±4964415a=7±73564415a=7±9115

 

1.

a=7+9115b=14a=14(7+9115)b=79115

 

2.

a=79115b=14a=14(79115)b=7+9115

 

laugh

Jul 12, 2021

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