Помогите решить пример по алгебре

$\frac{x^2}{x^2+7xy}: \frac{1}{x^2-49y^2}= \frac{x^2}{x(x+7y)}: \frac{1}{x^2-(7y)^2}= \frac{x}{(x+7y)}: \frac{1}{(x-7y)(x+7y)}= \\ = \frac{x}{(x+7y)}*\frac{(x-7y)(x+7y)}{1}= \frac{x}{1}*\frac{(x-7y)1}{1}= x(x-7y)=x^2-7xy$

(3-7√2)²-7(3-7√2)(9-√2)=3²-2*3*7√2+(7√2)²-7(3*9-3√2-7√2*9+7√2√2)=
=9-42√2+49*2-7(27-3√2-63√2+7*2)=9-42√2+98-7(27-66√2+14)=
=-42√2+107-7*27+7*66√2-7*14=-42√2+107-189+462√2-98=420√2-180