Помогите с решением,не понимаю ничего

5
√125+∛8*√5-5√49=5√5+2√5-5*7=7√5-35
6
(∛a+∛b)³/[(∛a+∛b)(∛a²-∛ab+∛b²)+∛ab(∛a+∛b)]+
+(∛a-∛b)³/[(∛a-∛b)(∛a²+∛ab+∛b²)-∛ab(∛a+∛b)]=
=(∛a+∛b)³/(∛a+∛b)(∛a²-∛ab+∛b²+∛ab)+(∛a-∛b)³/(∛a-∛b)(∛a²+∛ab+∛b²-∛ab)=
=(∛a+∛b)²/(∛a²+∛b²)+(∛a-∛b)²/(∛a²+∛b²)=
=(∛a²+2∛ab+∛b²+∛a²-2∛ab+∛b²)/(∛a²+∛b²)=(2∛a²+2∛b²)/(∛a²+∛b²)=
=2(∛a²+∛b²)/(∛a²+∛b²)=2
7
$\sqrt{( \sqrt{a^2+1} +1)^2}- \sqrt{( \sqrt{a^2+1} -1)^2} = \sqrt{a^2+1} +1- \sqrt{a^2+1} +1=2$