(2ax+1/2bx)^2
color(white)(aaaaaaaaaaaaa)2ax+1/2bx
color(white)(aaaaaaaaaaa) xx underline(2ax+1/2bx)
color(white)(aaaaaaaaaaaaa)4a^2x^2+abx^2
color(white)(aaaaaaaaaaaaaaaaaaaa)abx^2+1/4b^2x^2
color(white)(aaaaaaaaaaaaa)overline(4a^2x^2+2abx^2+1/4b^2x^2)
color(white)(aaaaaaaaaaaaa):.=(4a^2x^2+2abx^2+1/4b^2x^2)xx4/4
color(white)(aaaaaaaaaaaaa):.=(16a^2x^2+8abx^2+b^2x^2)/4
color(white)(aaaaaaaaaaaaa):.color(magenta)(=(x^2(16a^2+8ab+b^2))/4