Remember that the absolute value of any quantity is positive. To solve an equation involving absolute value, remember to solve the positive case and the negative case.
For example |x + 5| = 10, the positive case is x + 5 = 10 and the negative case is x + 5 = -10. Therefore, the solutions are x = 5 or x = -15.
The graph of the function f(x) = |ax + b| where a and b are real numbers will always fall in the first and second quadrants since absolute value is always positive.
The graph of the function f(x) = c|ax + b| where a and b are real numbers and c is negative will be in the third and fourth quadrants.