Question 997727
let x represent the ph of the water.


|x - 7.4| <= .2


when (x - 7.4) is positve, the equation becomes (x - 7.4) <= .2 which results in x <= 7.6


when (x - 7.4) is negative, the equation becomes (x - 7.4) >= -.2 which results in x >= 7.2


you reverse the inequality and you change the sign of the expression on the right when (x - 7.4) is negative.


there's a valid reason for doing this that i won't get into unless you ask.
it involves the basic definition of absolute value.


you get x <= 7.6 and x >= 7.4.


this can be written as 7.4 <= x <= 7.6


this means that the ph is good if it reads from 7.4 to 7.6 and not good otherwise.