If |m+n|=|m-n|, then m*n must be equal to:
Choose one
A) -3
B) 0
C) -2
D) -4
E) -5
Solution 1: Distance perspective   |m-n| = |m+n| ==&gt; The distance of m and n is equal to the distance of m and -n.   &lt;=======(-n)=======0=======(n)======&gt;   Only 0 is the value that has a distance equal to n and -n.   Solution 2:   |m-n| = |m+n| (square both)   m^2 -2mn + n^2 = m^2 + 2mn + n^2   4mn = 0   mn = 0   Answer: 0
<result>B</result>
If |m+n|=|m-n|, then m*n must be equal to: