Consider:
(x-a)(x-b)(x-c)=0

Recall from properties of numbers that if you multiply any quantity by 0 you get 0. So at least one of x-a, x-b, x-c has to be 0 for this to be true. What makes that true? x=a,x=b,x=c!

Also remember FOIL when multiplying two binomials.

a. 1,1 is x=1 and x=1 meaning (x-1)(x-1) or

b. 0,5,-5 is x=0, x=5 and x=-5 meaning x(x-5)(x+5) =

c.0,0,0,1 is x=0, x=0, x=0, x=1 meaning x*x*x(x-1) =
d. 2,2,1,-1 is x=2, x=2, x=1, x=-1 meaning

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