Tham khảo câu trả lời từ Trợ lý ảo Lazi To solve the equation \(|x+5| + |x+1| = 7\), we need to consider the critical points where the expressions inside the absolute values change sign. The critical points for this equation are \(x = -5\) and \(x = -1\). We will consider three cases based on these points: ### Case 1: \(x < -5\) In this case, both \(x + 5\) and \(x + 1\) are negative, so we have: \[ |x+5| = -(x+5) = -x - 5, \] \[ |x+1| = -(x+1) = -x - 1. \] Substituting these into the equation gives: \[ (-x - 5) + (-x - 1) = 7, \] which simplifies to: \[ -2x - 6 = 7. \] Solving for \(x\): \[ -2x = 7 + 6, \] \[ -2x = 13, \] \[ x = -\frac{13}{2} = -6.5. \] Since \(-6.5 < -5\), this solution is valid in this interval. ### Case 2: \(-5 \leq x < -1\) In this case, \(x + 5\) is non-negative and \(x + 1\) is negative. Therefore: \[ |x+5| = x + 5, \] \[ |x+1| = -(x+1) = -x - 1. \] Substituting these into the equation gives: \[ (x + 5) + (-x - 1) = 7, \] which simplifies to: \[ 5 - 1 = 7, \] \[ 4 = 7. \] This is not true, so there are no solutions in this interval. ### Case 3: \(x \geq -1\) In this case, both \(x + 5\) and \(x + 1\) are non-negative. Therefore: \[ |x+5| = x + 5, \] \[ |x+1| = x + 1. \] Substituting these into the equation gives: \[ (x + 5) + (x + 1) = 7, \] which simplifies to: \[ 2x + 6 = 7. \] Solving for \(x\): \[ 2x = 7 - 6, \] \[ 2x = 1, \] \[ x = \frac{1}{2}. \] Since \(\frac{1}{2} \geq -1\), this solution is valid in this interval. ### Summary of solutions The solutions to the equation \(|x+5| + |x+1| = 7\) are: \[ x = -6.5 \quad \text{and} \quad x = \frac{1}{2}. \] Therefore, the final answer is: \[ x = -\frac{13}{2}, \quad \text{and} \quad x = \frac{1}{2}. \]