Упростить выражения 80 баллов

А) (с+1/с)²-2=с²+2*с*1/с+(1/с)²-2=с²+2+1/с²-2=с²+1/с²

б)(m-2/m)²-(m+2/m)²=(m-2/m-(m+2/m))(m-2/m+m+2/m)=
(m-2/m-m-2/m))2m= -4/m*2m=-8

в)
$( \frac{x}{y} + \frac{y} {x})^2-( \frac{x^2}{y^2} + \frac{y^2} {x^2})=( \frac{x}{y})^2+2* \frac{x}{y} *\frac{y} {x} + (\frac{y} {x})^2- \frac{x^2}{y^2} - \frac{y^2} {x^2}= \\ = \frac{x^2}{y^2}+2* \frac{xy}{yx} + \frac{y^2} {x^2}- \frac{x^2}{y^2} - \frac{y^2} {x^2}=2* \frac{xy}{yx} =2$

г)
$(a+ \frac{a+1}{a})^2- (a- \frac{a+1}{a})^2= \\ (a+ \frac{a+1}{a}- (a- \frac{a+1}{a}))*(a+ \frac{a+1}{a}+ (a- \frac{a+1}{a}))= \\ (a+ \frac{a+1}{a}- a+ \frac{a+1}{a})*(a+ \frac{a+1}{a}+ a- \frac{a+1}{a})= \\ ( \frac{a+1}{a}+ \frac{a+1}{a})*(a+ a)= \frac{2(a+1)}{a}*2a=4(a+1)=4a+4$