题目

Have you ever thrown away a bottle of water? Maybe a bottle of water does not seem like much to you, but it can save the day for people who live in drought-hit* areas in China. In the past few months, some places in southeast China has experienced a serious drought. In Yunnan, Guangxi, Sichuan, Guizhou and Chongqing, there has been very little rain since last autumn. Crops have died. The land has cracked* and wells and rivers have dried up. More than 20 million people are having difficulty finding safe drinking water. After learning about the drought, many people across the country have 已知x=1为奇函数f（x）=13ax3+bx2+（a2-6）x的极大值点，（1）求f（x）的解析式；（2）若P（m，n）在曲线y=f（x）上，证明：过点P作该曲线的切线至多存在两条．