



 
Hi Rosa, If the coefficients have to be integers then the most you can do is \[9x^2  12y^2 = 3\left(3 x^2  4 y^2\right).\] If this problem comes from a high school text book then this is probably what is expected. If it is not required that the coefficients be integers then you can write \[9x^2  12y^2 = \large \left( 3x\right)^2  \normalsize \left(\sqrt{12} y\right)^2\] and factor it as a difference of squares. Penny  


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