Odpowiedź :
[tex](3x+1)^2=(3x)^2+2\cdot3x\cdot 1+1^2=9x^2+6x+1\\\\ (5x+4y)^2=(5x)^2+2\cdot5x\cdot4y+(4y)^2=25x^2+40xy+16y^2\\\\(a+9y)^2=a^2+2\cdot a\cdot9y=a^2+18ay+81y^2[/tex]
[tex](3x+1)^2=(3x)^2+2\cdot3x\cdot 1+1^2=9x^2+6x+1\\\\ (5x+4y)^2=(5x)^2+2\cdot5x\cdot4y+(4y)^2=25x^2+40xy+16y^2\\\\(a+9y)^2=a^2+2\cdot a\cdot9y=a^2+18ay+81y^2[/tex]