Solve: xy=−30, x+y=13

Cael Dickerson

Cael Dickerson

Answered question

2022-11-04

Solve:
x y = 30
x + y = 13

Answer & Explanation

barene55d

barene55d

Beginner2022-11-05Added 23 answers

We have in general
( x + y ) 2 4 x y = ( x y ) 2 .
In our case that gives ( x y ) 2 = 289, so x y = ± 17
Now solve the system x + y = 13, x y = 17 and the system x + y = 13 x y = 17.
Nola Aguilar

Nola Aguilar

Beginner2022-11-06Added 4 answers

Start with
x + y = 13 y = 13 x
so that
30 = x y = x ( 13 x ) = 13 x x 2 x 2 13 x 30 = 0
which solves to give x = 2 and x = 15. The corresponding 𝑦 values are 15 and 2.

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