已知a+b=5,ab=7,求(a²+b²)/2,a²-ab+b²的值.
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/02 17:49:06
![已知a+b=5,ab=7,求(a²+b²)/2,a²-ab+b²的值.](/uploads/image/z/1573797-21-7.jpg?t=%E5%B7%B2%E7%9F%A5a%2Bb%3D5%2Cab%3D7%2C%E6%B1%82%EF%BC%88a%26%23178%3B%2Bb%26%23178%3B%EF%BC%89%2F2%2Ca%26%23178%3B-ab%2Bb%26%23178%3B%E7%9A%84%E5%80%BC.)
已知a+b=5,ab=7,求(a²+b²)/2,a²-ab+b²的值.
已知a+b=5,ab=7,求(a²+b²)/2,a²-ab+b²的值.
已知a+b=5,ab=7,求(a²+b²)/2,a²-ab+b²的值.
(a²+b²)/2
=[(a+b)^2-2ab]/2
=[25-14]/2=11/2
a²-ab+b²
=(a+b)^2-3ab
=25-21
=4
(a²+b²)/2=[(a+b)²-2ab]/2=[5²-2*7]/2=5.5
a²-ab+b²=a²+2ab+b²-3ab=(a+b)²-3ab=4
(a²+b²)/2=[(a+b)²-2ab]/2=(25-14)/2=5.5
a²-ab+b²=a²+b²-ab=25-14-7=4