[tex]\it \underline{\underline{(a+b)^2=a^2+2ab+b^2}}\\ \\ \\ (x+4)^2=x^2+2\cdot x\cdot4+4^2=x^2+8x+16\\ \\ (2x+7)^2=(2x)^2+2\cdot2x\cdot7+7^2=4x^2+28x+49\\ \\ \\ \underline{\underline{(a-b)^2=a^2-2ab+b^2}}\\ \\ \\ (x-2)^2=x^2-2\cdot x\cdot2+2^2=x^2-4x+4\\ \\ (2x-3)^2=(2x)^2-2\cdot2x\cdot3+3^2=4x^2-12x+9[/tex]
