Find the following product:

To find the product, we will use distributive law as follows:

4. $1 x y(1.1 x-y)$

$=(4.1 x y \times 1.1 x)-(4.1 x y \times y)$

$=\{(4.1 \times 1.1) \times x y \times x\}-(4.1 x y \times y)$

$=\left(4.51 x^{1+1} y\right)-\left(4.1 x y^{1+1}\right)$

$=4.51 x^{2} y-4.1 x y^{2}$

Thus, the answer is $4.51 x^{2} y-4.1 x y^{2}$.