Tuesday, 11 October 2016

algebra precalculus - Given $frac {acdot y}{bcdot x} = frac CD$, find $y$.



That's a pretty easy one... I have the following equality : $\dfrac {a\cdot y}{b\cdot x} = \dfrac CD$ and I want to leave $y$ alone so I move "$b\cdot x$" to the other side



$$a\cdot y= \dfrac {(C\cdot b\cdot x)}{D}$$




and then "$a$"



$$y=\dfrac {\dfrac{(C\cdot b\cdot x)}D} a.$$



Where is my mistake? I should be getting $y= \dfrac {(b\cdot C\cdot x)}{(a\cdot D)}$.



I know that the mistake I am making is something very stupid, but can't work it out. Any help? Cheers!


Answer



No mistake was made. Observe that:
$$

y=\dfrac{\left(\dfrac{Cbx}{D}\right)}{a}=\dfrac{Cbx}{D} \div a = \dfrac{Cbx}{D} \times \dfrac{1}{a}=\dfrac{Cbx}{Da}=\dfrac{bCx}{aD}
$$
as desired.


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