jmc

Using the difference of squares factorization individually on the first pair of terms and the second pair of terms, we have $$\begin{array}{rl}1002^2& -502^2+298^2-202^2\\ & =(1002+502)(1002-502)+(298+202)(298-202)\\ & =(1504)(500)+(500)(96)\\ & =(500)(1504+96)\\ & =(500)(1600)\\ & =\boxed{800000}.\end{array}$$