Mathematics
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OpenStudy (anonymous):
Solve Each Equation.
1/x+1/2x=1/6
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OpenStudy (mathlegend):
@Mertsj can you help here? This person isn't online... but I want to know if I am solving this right.
OpenStudy (mertsj):
\[\frac{1}{x}+\frac{1}{2x}=\frac{2}{2x}+\frac{1}{2x}=\frac{3}{2x}\]
OpenStudy (mertsj):
So we have the proportion:
\[\frac{3}{2x}=\frac{1}{6}\]
OpenStudy (mertsj):
Cross multiply and solve.
OpenStudy (mathlegend):
Wait but... when you multiplied you multiplied by the 2 in the denominator though right?
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OpenStudy (mertsj):
\[\frac{1}{x}\times \frac{2}{2}=\frac{2}{2x}\]
OpenStudy (mertsj):
So I replaced 1/x with 2/2x
OpenStudy (mertsj):
Then since the denominators of the two fractions are the same, you can add them by adding the numerators.
OpenStudy (mathlegend):
\[2(\frac{ 1 }{ 2 }x) = x\]
OpenStudy (mathlegend):
Can I show you what I was trying to do?
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OpenStudy (mertsj):
That is true.
OpenStudy (mertsj):
yes
OpenStudy (mathlegend):
\[2(\frac{ 1 }{ x } + \frac{ 1 }{ 2 }x = \frac{ 1 }{ 6 })\]
OpenStudy (mathlegend):
\[\frac{ 2 }{ x } + x = \frac{ 1 }{ 3 }\]
OpenStudy (mathlegend):
Right so far?
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OpenStudy (mathlegend):
Could this work?
OpenStudy (mertsj):
I am confused about what the original problem is
OpenStudy (mertsj):
Is it this:
\[\frac{1}{x}+\frac{1}{2x}=\frac{1}{6}\]
OpenStudy (mertsj):
or
\[\frac{1}{x}+\frac{1}{2}x=\frac{1}{6}\]
OpenStudy (mathlegend):
I believe so.
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OpenStudy (mathlegend):
Oh, I mean the 2nd one
OpenStudy (mertsj):
So what you have written is correct.
OpenStudy (mertsj):
\[\frac{2}{x}+x=\frac{1}{3}\]
OpenStudy (mathlegend):
\[x(\frac{ 2 }{ x } + x = \frac{ 1 }{ 3 })\]
OpenStudy (mertsj):
yes
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OpenStudy (mathlegend):
\[2+x ^{2}=\frac{ 1 }{ 3 }x\]
OpenStudy (mertsj):
yes
OpenStudy (mathlegend):
Now I am stuck...
OpenStudy (mathlegend):
because I have x^2...
OpenStudy (mertsj):
Multiply both sides by 3
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OpenStudy (mathlegend):
\[6 + 3x ^{2} = x\]
OpenStudy (mertsj):
yes. Now subtract x from both sides.
OpenStudy (mathlegend):
\[3x ^{2}-x+6\]
OpenStudy (mathlegend):
set equal to 0
OpenStudy (mertsj):
=0
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OpenStudy (mertsj):
Now use the quadratic formula because I don't think it will factor.
OpenStudy (mathlegend):
ok
OpenStudy (mathlegend):
\[\frac{ 1\pm {71i} }{ 6 }\]
OpenStudy (mathlegend):
?
OpenStudy (mertsj):
sqrt71
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OpenStudy (mathlegend):
\[\frac{ 1\pm \sqrt{-71} }{ 6 }\]
OpenStudy (mathlegend):
but we can't have a negative under the radical because it is imaginary right?
OpenStudy (mertsj):
\[\frac{1\pm \sqrt{71}i}{6}\]
OpenStudy (mathlegend):
Oh, haha... thank you :)
OpenStudy (mertsj):
yw. But it might have been easier to clear all the fractions right at the beginning by multiplying by the common denominator which is 6x
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OpenStudy (mertsj):
\[6x \times\frac{1}{x}\times+6x \times \frac{1}{2}x=6\times\frac{1}{6}\]
OpenStudy (mertsj):
\[6+3x^2=x\]
OpenStudy (mertsj):
\[3x^2-x+6=0\]
OpenStudy (mathlegend):
oh I see
OpenStudy (mertsj):
Good.