I am told to set the imaginary part of the following equation to 0 so I can find a value of C. I have values already for the other variables. What equation would I attain? All help appricaited.

[ -jR^2/ωC+RL/C+R/ωC (1/ωC-ωL)+j L/C (1/ωC-ωL)]/[R^2+(1/ωC-ωL)^2]