[tex]\displaystyle\bf\\8x^{2} +24xy+18y^{2} =2\cdot(4x^{2} +12xy+9y^{2} )=\\\\=2\cdot\Big[(2x)^{2} +2\cdot 2x\cdot 3y+(3y)^{2} \Big]=2\cdot(2x+3y)^{2} =\\\\=2\cdot(2x+3y)\cdot(2x+3y)[/tex]