题目

My mom's entire life changed in the matter of a few seconds.While driving home late one night，my parents' SUV was hit from behind by a drunk driver traveling 70 miles per hour.Dad was killed instantly.Mom was thrown from the SUV and people found her on the side of the road. Once I saw my mom in the hospital，I knew she had a long road ahead of her.She had crushing injuries to her arm and shoulder，and her elbow was dislocated in three places，leaving it permanently bent. Although it took my mom a long time to physically recover from the   accident，it was only a short time before在等比数列{an}中，若a1+a2+a3+a4=，a2a3=-，则+++=    ．