Hello guys, I am confused about when we can multiply and divide by the variable. I know the if zero is hidden as a factor then we can not divide or multiply. eg. x/2x+1=0 are we allowed to divide both side 2x+1. Although zero is hidden value of x, there are no other ways to solve this equation. Another eg. cos(x)((-4sin^2(x)-1)=0 if we pluck x=0 into the equation, we will see it will not satisfy the equation so this shows x does not take the value of zero, does this mean that we can divide the equation by the variable by the variable.. and also are allowed divide zero by the variable?