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Mathematics 18 Online
OpenStudy (anonymous):

x^3-9x^3/2+8=0

OpenStudy (mathstudent55):

Do you mean: \[x ^{3} - \frac{ 9x ^{3} }{ 2 } + 8 = 0\]

OpenStudy (shamim):

\[x ^{3}-9x ^{(3/2)}+8=0\]

OpenStudy (anonymous):

@shamim yeah, that's what I mean

OpenStudy (shamim):

\[or, x ^{3}-8x ^{(3/2)}-x ^{(3/2)}+8=0\]

OpenStudy (shamim):

\[x ^{(3/2)}(x ^{(3/2)}-8)-(x ^{(3/2)}-8)=0\]

OpenStudy (shamim):

\[or, (x ^{(3/2)}-1)(x ^{3/2}-8)=0\]

OpenStudy (anonymous):

\[I got this far (u-8)(u-1)=0 then u=8 u=1 \]

OpenStudy (shamim):

ok

OpenStudy (anonymous):

It says the answer is x=1and x=4 but I was wondering how the 4 came about.

OpenStudy (shamim):

\[\let x ^{3/2}=u\]

OpenStudy (shamim):

ok i m now trying to clearifying ur problem

OpenStudy (anonymous):

This is what I did: u^2-9u+8=0 then (u-8)(u-1)=0 factored. so u=8 and u=1 but then how did the text get x=4?

OpenStudy (shamim):

ok

OpenStudy (shamim):

let \[x ^{3/2}=u\]

OpenStudy (shamim):

then our equation will b \[u ^{2}-9u+8=0\]

OpenStudy (shamim):

\[or, u ^{2}-8u-u+8=0\]

OpenStudy (shamim):

\[or, u(u-8)-(u-8)=0\]

OpenStudy (shamim):

\[or, (u-1)(u-8)=0\]

OpenStudy (shamim):

\[u-1=0 \]

OpenStudy (shamim):

\[or, u=1\]

OpenStudy (shamim):

\[or, x ^{3/2}=1\]

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