Hi Katie;
4x^{2}20x=0
We need to factor...
4x(x5)=0
Either 4x or (x5) equals 0.
If 4x=0, then x=0
If x5=0, then x=5
Or...
We can factor like this...
4x^{2}20x=0
(4x0)(x5)
If we FOIL...
FIRST...(4x)(x)=4x^{2}
OUTER...(4x)(5)=20x
INNER...(0)(x)=0
LAST...(0)(5)=0
4x^{2}20x=0
So...
(4x0)(x5)
Either parenthetical equation must equal zero.
If 4x0=0, then x=0
If x5=0, then x=5
Same result, different factoring approach.
11/23/2013

Vivian L.
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