a) \(4x^2-12x+9\)
\(=\left(2x\right)^2-2.2x.3+3^2\)
\(=\left(2x-3\right)^2.\)
Chúc bạn học tốt!
c, \(4x^4+81\)
\(=4x^4+81+36x^2-36x^2\)
\(=\left(2x^2+9\right)^2-36x^2\)
\(=\left(2x^2+9-6x\right)\left(2x^2+9+6x\right)\)
a, \(4x^2-12x+9\)
\(=\left(2x\right)^2-12x+3^2\)
\(=\left(2x+3\right)^2\)
b, \(\left(a+b+c\right)^2+\left(a-b+c\right)^2-4b^2\)
\(=a^2+b^2+c^2+2ab+2ac+2bc-2ab-2bc+ac-4b^2\)
\(=2a^2-2b^2+2c^2+4ac\)
\(=2\left[\left(a^2+2ac+c^2\right)-b^2\right]\)
\(=2\left[\left(a+c\right)^2-b^2\right]\)
\(=2\left(a+c-b\right)\left(a+b+c\right)\)
