2次更式题,希望快速解答30分
a+b=更号里面(5-2倍更号6);a-b=更号里面(5+2倍更号6),求ab的值,要过程
参考答案:a+b = √(5-2√6) (a+b)^2 = 5-2√6 = a^2+b^2 +2ab…………(1)
a-b = √(5+2√6) (a-b)^2 = 5+2√6 = a^2+b^2 -2ab…………(2)
(1)-(2) = 4ab = -4√6
所以ab=-√6
a+b=更号里面(5-2倍更号6);a-b=更号里面(5+2倍更号6),求ab的值,要过程
参考答案:a+b = √(5-2√6) (a+b)^2 = 5-2√6 = a^2+b^2 +2ab…………(1)
a-b = √(5+2√6) (a-b)^2 = 5+2√6 = a^2+b^2 -2ab…………(2)
(1)-(2) = 4ab = -4√6
所以ab=-√6