Mathematics
6 Online
OpenStudy (anonymous):
solve
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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\[p^2(q^2+1)=7+y\]
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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 ?
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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)
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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 :
\(p+q = 3\)
\(p^2q^2 = 4\)
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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
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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