Chapter 9 - Solving Quadratic Equations - 9.3 - Solving Quadratic Equations Using Square Roots - Exercises - Page 501: 31

The error is in taking the square root of $x^{2}$. The square root of $x^{2}=36$ can be $x=-6$ or $x=6$. In the given solution, only positive value is considered. But the correct solution is $x=\pm 6$.

The error is in taking the square root of $x^{2}$. The square root of $x^{2}=36$ can be $x=-6$ or $x=6$. In the given solution, only positive value is considered. But the correct solution is $x=\pm 6$.