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what does an answer of {} mean?

 

when I type solve(a,b,ab=76,a+b=18), I get {} as an answer.

 Oct 5, 2017
 #1
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 a b = 76..........(1)

a+b=18............(2)

 

From (2) a = 18 - b   sub into (1)

b(18 -b) =76

18b - b^2 =76       re-arrange

-b^2 + 18b - 76 =0, solve for b

b =9 + sqrt(5), and b=9 - sqrt(5)   sub into (2)

a + (9 + sqrt(5) =18

a = 9 - sqrt(5)   and  a =9 + sqrt(5)

 Oct 5, 2017

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