Start by remembering that the square root symbol gives the non-negative root. The equation says that √(x + 1) is 3. To remove the square root, square both sides: x + 1 = 3² = 9. Now isolate x by moving the constant to the other side, so x = 9 - 1 = 8. Always check radical equations: substituting x = 8 makes the expression inside the root equal to 9, and √9 = 3. So the correct answer is 8.