You can use the commutative property of multiplication to convince your friend that changing the order of the numbers is a valid way to simplify the problem. The commutative property states that the order in which you multiply two numbers does not affect the product. In other words, for any numbers \( a \) and \( b \), \( a \times b = b \times a \).
Since multiplication is associative as well, you can also group the numbers in a way that makes the calculations easier. For example, you could multiply the two negative numbers first, which will give you a positive result, and then multiply that result with the other two numbers.
So, you could rearrange the multiplication as follows:
\[ (-4) \times (-34) \times (57) \times (715) = (4) \times (34) \times (57) \times (715) \]
This shows that your method is valid, and it can lead to a simpler calculation.