Lauren and Michael were working on the same math problem. Identify which student is incorrect and explain the error.

Lauren                                                Michael
​Solve: x² + x​ - 2​ = 0 ​ Solve: ​ x² + x​ - 2​ = 0
 x² + 2x​ - x​ - 2​ = 0 ​ x² + 2x​ - x​ - 2​ = 0
x(x +​ 2) -1(x​ + 2)​ = 0 ​ x(x +​ 2) -1(x​ + 2)​ = 0
​ (x -​ 1)(x +​ 2) = 0 ​ (x -​ 1)(x +​ 2) = 0
 x​ = 1 or x​ = -2 x​ = -1 or x​ = 2

1 answer

Lauren is incorrect. In the second step, she combined the x terms incorrectly. It should be x² + 2x - x - 2, which simplifies to x² + x - 2. The later steps are correct for both students.