If you have two negatives they cancel each other out and make a positive. The same if you have to positives the product will be positive. If you have a negative and a positive you multiply the numbers and bring down the negative. Same if you have a positive and a negative. Only two negatives cancel each other out, same with positives. For example -4(-5)(-1) you would use order of operations, 4 and the 5 cancel each other out and you multiply 20 by -1 which is -20 since you bring down the negative.
