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Mathematics 7 Online
OpenStudy (fionacndg):

Help! Algebra! Will fan and medal

OpenStudy (fionacndg):

Given that f(x) = x2 + 3x + 6 and g(x) = the quantity of \[\frac{ x-3 }{ 2 }\] , solve for f(g(x)) when x = 1.

OpenStudy (fionacndg):

possible answers: -1 0 3

OpenStudy (fionacndg):

and 4

OpenStudy (kirbykirby):

\[ f(\color{red}{x})=\color{red}{x}^2+3\color{red}{x}+6\\ f(\color{red}{g(x)})=(\color{red}{g(x)})^2+3(\color{red}{g(x)})+6\] Substitute g(x) for your given expression into the equation. Then to get f(g(x)) when x =1, use the above result and substitute x=1 wherever you see x

OpenStudy (fionacndg):

Okay, I wrote that all down... So next, solve for f(x) ?

OpenStudy (kirbykirby):

plug in x=1 into your f(g(x)) expression

OpenStudy (fionacndg):

so the f(g(x)) equation equals 10

OpenStudy (kirbykirby):

\[f(\color{red}{g(x)})=(\color{red}{g(x)})^2+3(\color{red}{g(x)})+6\] since \(g(x)=\dfrac{x-3}{2}\), then: \[f(\color{red}{g(x)})=\left(\color{red}{\dfrac{x-3}{2}}\right)^2+3\left(\color{red}{\dfrac{x-3}{2}}\right)+6 \] Is that what you got? You just need to plug in x=1 now. It shouldn't give 10

OpenStudy (fionacndg):

I got 4.75

OpenStudy (kirbykirby):

that's closer to the answer... but not quite.

OpenStudy (fionacndg):

Oh.. okay just give me a second to redo my work...

OpenStudy (fionacndg):

OHHH its 4

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