Question 911961
The idea is to factor as much as possible. Afterwards, cancel out the common terms between the numerator and denominator.


{{{(r^2-9)/(r^2-6r+9)}}}


{{{(r^2-3^2)/(r^2-6r+9)}}}


{{{((r-3)(r+3))/(r^2-6r+9)}}}


{{{((r-3)(r+3))/((r-3)(r-3))}}}


{{{(highlight((r-3))(r+3))/(highlight((r-3))*(r-3))}}}


{{{(cross((r-3))(r+3))/(cross((r-3))*(r-3))}}}


{{{(r+3)/(r-3)}}}


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So, {{{(r^2-9)/(r^2-6r+9)}}} simplifies to {{{(r+3)/(r-3)}}}