б) (0,9x + 1\frac{13}{27}y )^2; г) (-2,3а +1\frac{2}{23}b )^2.

б)

${(\mathrm{0,9}x+1\frac{13}{27}y)}^2={\left(\frac{9}{10}x\right)}^2+2·\frac{9}{10}x·\frac{40}{27}y+{\left(\frac{40}{27}y\right)}^2=\frac{81}{100}{x}^2+\frac{4}{3}xy+\frac{1600}{729}{y}^2$

г)

${(-\mathrm{2,3}a+1\frac{2}{23}b)}^2={(-\frac{23}{10}a)}^2+2·(-\frac{23}{10}a)·\frac{25}{23}b+{\left(\frac{25}{23}b\right)}^2=\frac{529}{100}{a}^2-5ab+\frac{625}{529}{b}^2$

Ответ: б) $$\frac{81}{100}x^2 + \frac{4}{3}xy + \frac{1600}{729}y^2$$; г) $$\frac{529}{100}a^2 - 5ab + \frac{625}{529}b^2$$