Final answer:
To find the sum of the given expression, combine the fractions over a common denominator and simplify the numerator and denominator.
Step-by-step explanation:
To find the sum of the given expression, we need to combine the two fractions over a common denominator. The common denominator in this case is (7x - y)(y - 7x). We can rewrite the expression as follows:
5x/(7x - y) + 4/(y - 7x) = (5x*(y - 7x) + 4*(7x - y))/((7x - y)(y - 7x))
Expanding and simplifying the numerator gives:
(5xy - 35x^2 + 28x - 4y)/(y^2 - 49x^2)
This is the simplified form of the sum.