Question 141587
Math tutors I don't know how to do this..thank you
Find an equation of variation where y varies jointly as x and z and		 	inversely as the square of w and y=20 when x=-0.5, z=4, and w=5.
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Start with this formula for the equation of variation:

{{{Letter_that_varies = k((all_directlys_and_jointlys_or_1_if_none)/(all_inverselys_or_1_if_none))}}}

The letter that varies is {{{y}}}.
The "jointlys" are {{{x}}} and {{{z}}}
The only "inversely" is {{{w^2}}}

So plug in:

{{{y=k((xz)/w^2)}}}

Plug in the given values y=20 when x=-0.5, z=4, and w=5.

{{{20=k((-0.5(4))/(5)^2))}}}

{{{20=k((-2)/25))}}}

Multiply both sides by 25

{{{500=k(-2)}}}

{{{500=-2k}}}

{{{-250=k}}}

Now substitute {{{-250}}} for {{{k}}} in

{{{y=k((xz)/w^2)}}}

{{{y=-250((xz)/w^2)}}}

Edwin</pre>