导数已为大家所熟知,在导数的四则运算中,两函数的积和商的导数计算公式的应用在解题中时有出现,其中以导数为工具构造函数来解决问题更是重点,也是难点,那么怎样合理的构造函数就是解决问题的关键.两函数的积的导数计算公式[f(x)·g(x)]′=f′(x)·g(x)+f(x)·g′(x),充分抓住等式右边的结构特点,构造出等式左边的 Derivatives are well-known. In the four operations of derivatives, the application of the derivative formula for the sum-of-products of two functions occurs in solving problems. It is more difficult and more difficult to solve the problem with derivatives as a tool constructor , Then how to construct the function is the key to solve the problem. The derivative of the product of the two functions is calculated by the formula [f (x) · g (x)] ’= f’ (x) · g (x) + f g ’(x), take full advantage of the structural features to the right of the equation to construct the left side of the equation