Đề sai rồi bạn
Vế phải : \(\left(ax+aby+3cz\right)^2\)
\(=a^2x^2+a^2b^2y^2+9c^2z^2+2a^2bxy+6abcyz+6axcz\)
Vế trái : \(\left(x^2+2y^2+3z^2\right)\left(a^2+2b^2+3c^2\right)\)
\(=\left(x^2+2y^2+3z^2\right)a^2+\left(x^2+2y^2+3z^2\right)2b^2+\left(x^2+2y^2+3z^2\right)3c^2\)
\(=x^2a^2+2a^2y^2+3a^2z^2+2b^2x^2+4b^2y^2+6b^2z^2+3x^2c^2+6c^2y^2+9c^2z^2\)
Ko hề bằng nhau
\(\Rightarrow\)đề sai