Find the error in the following proof that 2 = 1. Consider the equation a = b. Multiply both sides by a to obtain a² = ab. Subtract b² from both sides to get a² − b² = ab − b². Now factor each side, (a + b)(a − b) = b(a − b), and divide each side by (a − b) to get a + b = b. Finally, let a and b equal 1, which shows that 2 = 1.