Help and explain pls

If 2(a^2+b^2)=(a+b)^2 then, > a+b=0, > ab=0, > a=b, > 2a=b

If f(x) = 6x – 4, what is f(x) when x = 8? a2 b16 c44 d52

X/y + 4y/x divided by x/y - 2y/x explain as in depth as you can how you simplfied the fractions. i don't know where to start on this : /