Library/Algebra/Absolute value/Equations with absolute values

Equations with absolute values

Overview
Important

To solve equations with absolute values, we consider the definition: A=B|A| = B means A=BA = B or A=BA = -B, provided B0B \geq 0. For more complex equations, like x2=5|x - 2| = 5, we set x2=5x - 2 = 5 or x2=5x - 2 = -5, so x=7x = 7 or x=3x = -3. For equations like 2x+1=x4|2x + 1| = |x - 4|, we consider both cases: 2x+1=x42x + 1 = x - 4 and 2x+1=(x4)2x + 1 = -(x - 4).

Important properties

  • If A=B|A| = B and B<0B < 0, there is no solution.

  • If A=B|A| = B and B0B \geq 0, solutions are A=BA = B or A=BA = -B.

  • For A=B|A| = |B|, solutions are A=BA = B or A=BA = -B.

  • Always check solutions in the original equation, especially if you square both sides.