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4x^2-20x=0

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1 Answer

Hi Katie;
4x2-20x=0
We need to factor...
4x(x-5)=0
Either 4x or (x-5) equals 0.
If 4x=0, then x=0
If x-5=0, then x=5
Or...
We can factor like this...
4x2-20x=0
(4x-0)(x-5)
If we FOIL...
FIRST...(4x)(x)=4x2
OUTER...(4x)(-5)=-20x
INNER...(0)(x)=0
LAST...(0)(-5)=0
4x2-20x=0
So...
(4x-0)(x-5)
Either parenthetical equation must equal zero.
If 4x-0=0, then x=0
If x-5=0, then x=5
Same result, different factoring approach.

Comments

Katie;
I forgot to check my work.
4x2-20x=0
If x=0
4(02)-20(0)=0
0-0=0
0=0
 
If x=5
4x2-20x=0
4(52)-20(5)=0
4(25)-100=0
100-100=0
0=0

Comment