Since this is categorized under PEMDAS, I'll answer in terms of the order of operations and assume that you have a calculator.
1000^2/(252^2-248^2) is a fancy way of writing (1000^2)div(252^2-248)^2. The P in PEMDAS stands for parentheses, and we have some parentheses, so let's work them out.
The first set of parentheses is 1000^2. Inside those parentheses, we go through PEMDAS again. There are no further parentheses, so we can move onto E: exponents, which there is! A calculator or mental math or a table will tell you that 1000^2=1000000. Now, we have 1000000 for our first set of parentheses and there's nothing else to do with that.
Our equation is now 1000000div(252^2-248^2). There are still parentheses, so we have to deal with those.
The second set of parentheses is 252^2-248^2. Let's go through PEMDAS. There's no further parentheses, but there are exponents. 252^2=63504, giving us 63504-248^2. There are still exponents, so we continue. 248^2=61504, giving us 63504-61504. There are no more exponents, so we can move on. MD stands for multiplication and division, from left to right. Neither operation is present here, so we finally get to AS, which stands for addition and subtraction from left to right. We subtract, finding that 63504-61504=200. So our answer for this section is 200.
Back to the entire equation, we now have 1000000div200. There are no more parentheses or exponents, but there is division. We find that 1000000div200=5000 Our equation is now 5000. There is no more multiplication nor division and there is no addition nor subtraction, therefore we know that we are done!
