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Mathematics 6 Online
OpenStudy (anonymous):

solve

OpenStudy (anonymous):

\[\sqrt{2x-1}+\sqrt{y+3}=3\] \[2xy+6x-y=7\]

OpenStudy (anonymous):

seems like (2)\[2x(y+3)-y=7\]

OpenStudy (anonymous):

\[p=\sqrt{y+3}\] \[q=\sqrt{2x-1}\]

OpenStudy (anonymous):

\[p+q=3\] \[(q^2+1)p=7+y\]

OpenStudy (anonymous):

no 2nd 1\[p^2(q^2+1)=7+y\]

OpenStudy (anonymous):

\[(pq)^2+p=7+p^2-3\]

OpenStudy (anonymous):

\[(pq)^2-p^2+p-4=0\] \[p+q=3\]

OpenStudy (anonymous):

hey once slow down and think,

OpenStudy (anonymous):

ok

OpenStudy (anonymous):

can sum of 2 positive irrational numbers give you a rational number ?

OpenStudy (anonymous):

no

OpenStudy (anonymous):

stickly speaking it can.. you think about it, in this case no it can not, so what are possible combinations fot 3..

OpenStudy (anonymous):

@hartnn

OpenStudy (anonymous):

\[p^2(p-3)^2-p^2+p-4=0\] \[p^4-6p^3+8p^2+p-4=0\]

OpenStudy (anonymous):

1+2, 2+1, 3+0,0+3 right, so out of possible (x,y) pairs are (1,1) satisfies both equations write (i am assuming you know tha traditional way to solve)

ganeshie8 (ganeshie8):

we should have eliminated the y also in the beginning

OpenStudy (anonymous):

\[p=1\] \[1=y+3,y=-2\] \[2=q,x=5/2\]

ganeshie8 (ganeshie8):

seconf equation we may rewrite as \(2xy + 6x - y = 7\) \(y(2x-1) + 6x = 7\) \(y(2x-1) + 3(2x-1) = 7-3\) \((2x-1)(y+3) = 4\)

OpenStudy (anonymous):

this is nice

ganeshie8 (ganeshie8):

then subbint p,q we get : \(p+q = 3\) \(p^2q^2 = 4\)

OpenStudy (anonymous):

but did you noticethat i eliminated y\[y=p^2-3\]

ganeshie8 (ganeshie8):

ha yes... i see nothing wrong in that method also

OpenStudy (anonymous):

but it made the equation clumsy

OpenStudy (anonymous):

\[p+q=3,pq=\pm 2\]

ganeshie8 (ganeshie8):

p >= 0, q >= 0 so we -2 we can ignore

OpenStudy (anonymous):

\[p^2-3p+2=0\] \[q^2-3q+2=0\]

OpenStudy (anonymous):

\[p=q=1,p=q=2,\]

OpenStudy (anonymous):

tired now i'll slve later

OpenStudy (anonymous):

dude it is p=1 and q=2

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