7) (4x/(x+2) + 2x) * (x+2)/4x^2 = (4x + 2x*(x+2))/(x+2) * (x+2)/4x^2 = (2x^2 + 8x)/(x+2) * (x+2)/4x^2 = (2x*(x+4)*(x+2))/(x+2)*4x^2 = (x+4)/2x
8) 3a/(1+c) - 4/(1-c^2) * (a-ac)/2 = 3a/(1+c) - 4/((1-c)*(1+c)) * (a(1-c))/2 = 3a/(1+c) - 2a/(1+c) = (3a-2a)/(1+c) = a/(1+c)