The rate law for the reaction is given by:
\[
\text{Rate} = k[\text{A}]^2
\]
Where:
- \( k \) is the rate constant,
- \( [\text{A}] \) is the concentration of reactant A.
If the concentration of A is increased by a factor of 3, then:
\[
[\text{A}] \rightarrow 3[\text{A}]
\]
Substitute this new concentration into the rate law:
\[
\text{Rate}_{\text{new}} = k(3[\text{A}])^2 = k \times 9[\text{A}]^2
\]
Thus, the rate of the reaction increases by a factor of 9.