⎩ ⎪ ⎪ ⎨ ⎪ ⎪ ⎧ x + x 2 + y 2 3 x − y y − x 2 + y 2 x + 3 y = = 3 0
Solve the system of equations for real values of ( x , y ) , and submit the sum of all values of ( x , y ) .
ie. If you have got pairs as ( 9 , 1 0 ) , ( 5 , 7 ) submit your answer as 9 + 1 0 + 5 + 7 .
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Great solution hats of to my thoughts
After looking at the solutions above and the ordered pairs they ended up with, I am having doubts about mine. Could someone please explain where I am going wrong?
x + x 2 + y 2 3 x − y = 2 a n d y − x 2 + y 2 x + 3 y = 0 Let z = x + i y Multiplying the second equation with i and adding, we get
z + ∣ z ∣ 2 ( 3 − i ) z ˉ = 3
= > z 2 + − 3 z + ( 3 − i ) = 0
= > z = 2 3 ± 9 − 4 ( 3 − i )
And this gives- x = 2 3 , i y = ± 2 9 − 4 ( 3 − i )
Here I took a leap of faith; without actually calculating y , I assumed that probably in adding all the solutions ( x , y ) they will cancel each other and I will end up adding 3 / 2 twice. Hence the answer is 3. Now, I am a little skeptic as to whether this is just a coincidence. Could someone please help? Thanks in advance.
Your leap of faith is somewhat incorrect. It just so happens that the ± parts cancel out in the sum of all parts, but it is not true that x = 2 3 , i y = ± 2 9 − 4 ( 3 − i ) . For example, if you were asked for ∑ ( x 2 + y 2 ) , then your approach would not work.
When you set z = 2 3 ± 9 − 4 ( 3 − i ) = x + i y , you needed to equate real and imaginary parts. What we have, is that 9 − 4 ( 3 − i ) = ( 1 + 2 i ) , and so we have z = 2 3 ± ( 1 + 2 i ) = 2 + i , 1 − i .
(2,1) and (1,-1) satisfies the above pair of equation . Put x=åcos(m) y=åsin(m) After solving both equations in a and m we get å^2=2 or 5 (real values) now we plugin the value of a and get m.
Now check which solutions are added because of squaring while solving for å by putting the values.
why don't you use l a t e x it will make the things beautiful
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Let z = x + i y . We have z ∗ = x − i y , i z ∗ = y + i x , z z ∗ = x 2 + y 2 .
Then, 3 + 0 i = x + i y + x 2 + y 2 3 x − 3 y i − y − x i = z + z z ∗ 3 z ∗ − i z ∗ = z + z 3 − i .
Clearly, z = 0 is not a solution, so we can multiply throughout by z to obtain z 2 − ( 3 ) z + ( 3 − i ) = 0 .
Factoring this, we get [ z − ( 1 − i ) ] [ z − ( 2 + i ) ] = 0 .
Thus, the only possible solutions are ( x , y ) = ( 1 , − 1 ) , ( 2 , 1 ) .
We can verify that these are indeed solutions to the original equations.