题目

For most of us, our house is our home base, and having a happy and pleasant vibe (氛围) in all of our rooms is important. 1. ... Adding color to any room can help you feel more cheerful, and it can be done pretty quickly! Consider painting just one wall a lively color. A bright red, a peaceful green or even a lively yellow completely changes the feel. 2. ... First of all, think flower power! Fresh flowers are very easy to get at your local grocery market, and they make any room seem more alive. Plants have the same positive effect. Another way to celebrate life is to surround yourself with 设函数f(x)=ax2+8x+3(a＜0),对于给定的负数a，有一个最大的正数l(a),使得在整个区间［0,l(a)］上，不等式|f(x)|≤5都成立.问a为何值时,l(a)最大？求出这个最大的l(a),证明你的结论.