Someone please answer this question about chemical EQ.
When you have a situation like

1x10^-9 = ((.004+2x)^2(x))/(1.9-2x)^2 we were taught to cancel out the substraction signs when we have a small number for Kc but they never did an explain with a +2x so do we cancel it out or not??

Question

Someone please answer this question about chemical EQ. 
When you have a situation like

1x10^-9 = ((.004+2x)^2(x))/(1.9-2x)^2 we were taught to cancel out the substraction signs when we have a small number for Kc but they never did an explain with a +2x so do we cancel it out or not??

aaronq · Answer

if they're less than 5% of the original then they can be considered negligible

anonymous · Answer

damn book keeps screwing me up thats what I thought!