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how many ordered pair of a,b integers are there with a+2a+5=b3.

 Jun 26, 2022
 #1
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Do not post A o P S homework.

 Jun 26, 2022
 #2
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Cross multiply: 3(a+2)=b(a+5)

 

Simplify: 3a+6=ab+5b

 

Isolate the constant: 3aab5b=6

 

Factor out a: a(3b)5b=6

 

Add 15 to both sides: a(3b)5b+15=9

 

Factor out b: a(3b)+5(3b)=9

 

Combine like terms: (a+5)(3b)=9

 

Note that a+5 must equal 1, 3, or 9, so 3b can equal the other factor of 9.

 

Thus, there are 3 cases that work.

 

Note that the cases are (4, 2), (-2, 0), and (-4, -6)

 Jun 26, 2022

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