(x/100-1)(x/100+1)=kx^2-1
(x/100-1)(x/100+1)=(x/100)^2 - 1^2 because it's a difference of squares ( (a-b)(a+b) = a^2-ab+ab-b^2 = a^2 - b^2):
(x/100)^2 - 1^2=kx^2 - 1
(x/100)^2 - 1=kx^2 - 1
(x/100)^2=kx^2
(x^2)/(100^2)=kx^2
1/(100^2)=k
1/10000=k
k=0.0001
