What adds to - 1 and multiplies to - 6

Either you're looking for "one number" that is added to - 1 and multiplied to - 6 to give "another number" which you didn't mention.

Or

You're looking for "two numbers" when added together they equal - 1 and when multiplied they make - 6.

In the second case, you're looking for:

2 and - 3

In the first case, you have to tell us the second number. So, I am guessing you're asking about the second case.