



 
Hi Mark, When you commonly see this is where you have an equation involving $x$ and $y$ and perhaps involving other variables and you are asked to write $y$ as an expression in terms of $x.$ This means that you are to manipulate the equation you have to obtain an equivalent equation of the form \[y = \mbox{ an expression containing x but not y.}\] For example suppose the original equation is $ x^2 + 3y  7  x  y = 0.$ First you only want terms containing $y$ on the left side of the equation so add $x^2 +7 + x$ to each side to get \[x^2 + 3y  7  x  y x^2 + 7 + x = x^2 +7 + x\] which simplifies to \[3y  y = x^2 +7 + x \mbox{ or } 2y = x^2 + x + 7.\] Multiplying each side by $\large \frac12$ yields \[y = \frac12 \left(x^2 + x + 7\right)\] which is equivalent to the original equation $ x^2 + 3y  7  x  y = 0$ but written as $y$ as an expression in terms of $x.$ I hope this helps,  


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