Question 246705
A negative exponent stands for a fraction.  Therefore, we may re-write the equation from: {{{w=cr^-2}}} to {{{w=(c/r^2)}}}
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Now multiply by {{{r^2}}} on both sides, we get:
{{{wr^2=c}}}
Then, mulitply by w on both sides:
{{{r^2=cw}}}
Then take the square root to find r:
{{{r=+sqrt(cw)}}} and {{{r=-sqrt(cw)}}}
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Done!