<PRE><B>Question 499304</B>
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

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