Use the ZERO PORDUCT PROPERTY. It states that if ab = 0, then either a = 0 or b = 0, or both a and b are 0. When the product of factors equals zero, one or more of the factors must also equal zero.
This means that each of these terms need to be set equal to zero. (N-1)(N+6)(N+5)=0. n-1=0, n+6=0, n+5=0 So..... N equals 1,-6,-5