\(\frac{12}{5}x^2y^2-9x^4-\frac{4}{25}y^4\)
\(=-\left(9x^4-\frac{12}{5}x^2y^2+\frac{4}{25}y^4\right)\)
\(=-\left[\left(3x^2\right)^2-2.3x^2.\frac{2}{5}y^2+\left(\frac{2}{5}y^2\right)^2\right]\)
\(=-\left(3x^2-\frac{2}{5}y^2\right)^2.\)
Chúc bạn học tốt!