Find two numbers a and b whose sum a+b is - 4 and whose difference a-b is - 4.

The answer is a = - 4 and b = 0.

We can solve this by looking at a system of equations using what was given

a + b = - 4

a - b = - 4

Then add then two equations together.

2a = - 8 - - - > then divide by 2 for your a value

a = - 4

You can then put that into the equation and solve for b.

-4 + b = - 4 - - - > add 4 to both sides

b = 0