SOLUTION: I need to find the solution to the equation {{{ 160z^2=640 }}} by factoring. I know the first step is to set the equation equal to zero by subtracting 640 from both sides, leaving

Question 499304: I need to find the solution to the equation by factoring. I know the first step is to set the equation equal to zero by subtracting 640 from both sides, leaving me with , and I then factored out the common factor, 80. I now have . I don't know where to go from there.
Found 2 solutions by chessace, Maths68:
Answer by chessace(471) (Show Source): You can put this solution on YOUR website!
First, 2 and 8 are both even, so 160 was a better factor.
And that factor can be thrown out (divide both sides by it).
So you are left with z^2-4=0
Factor that by recalling that (z+a)(z-a)=z^2-a^2

Answer by Maths68(1474) (Show Source): You can put this solution on YOUR website!
Instead of taking 80 common take 160 then equation will be
160(z^2-4)=0
Divide by 160 both sides of the above equation.
160(z^2-4)/160=0/160
z^2-4=0
z^2=4
Take squar root both sides
sqrtZ^2=sqrt4
z=2 or z=-2
OR
160z^2=640
Divide by 160 both sides of the above equation.
160(z^2)/160=640/160
z^2=4
Take squar root both sides
sqrtZ^2=sqrt4
z=2 or z=-2