Algebra
posted by Melvin .
The formula T=2π√L/480 can be used to find the period (T in seconds, the time it takes a pendulum to complete one cycle) of a pendulum that is L cm long.
(a)Rewrite this formula using rational exponents. Don't forget to rationalize the denominator.
(b)Solve the formula for L.

I think you mistyped 980
T=2PI (L/980)^.5
to solve for L, square both sides first. 
a. T = 2pi*sqrt(L/980).
Square both sides:
T^2 = 4(pi)^2(L/980).
b. Multiply both sides by 980/4(pi)^2:
980T^2/4(pi)^2 = L. 
Thanks Henry and bobpursley for replying. Now the question makes sense :)