Answer:
a + b = 16 or -16.
Explanation:
a - b = 4
ab = 60 so a = 60/b
Substituting for a in the first equation:
60/b - b = 4
60 - b^2 = 4b
b^2 + 4b - 60 = 0
(b + 10)b - 6) = 0
b = 6, -10.
Therefore, from the first equation:
When b = -10 . a + 10 =4 giving a = -6 or
When b = 6, a - 6 = 4 giving a = 10.
So when a = -6, b = -10 and
when a = 10, b = 6.
So a + b is either 16 or -16.