Algebra problem (-I*a)/R^2 - m*g = m*a solve for a?

saboohis

I know the answer is a = - g/ (1 + I/mR^2) but I dont know how to get there?

eugene

-la/R^2 - mg = ma

-mg = ma + la/R^2 (Add both sides by la/R^2)

-mg = a(m + l/R^2) (Factor the a on the right-hand side)

-g = a(1 + l/mR^2) (Divide both sides by m)

-g/(1 + l/mR^2) = a (Divide both sides by 1 + l/mR^2).