设a,b,c为△ABC的三边,求证：关于x的方程x²+2ax+b²＝0与x²-2cx-b²＝0有公共根的充要设a,b,c为△ABC的三边，求证：关于x的方程x²+2ax+b²＝0与x²-2cx-b²＝0有公共根的充要条

设a,b,c为△ABC的三边,求证：关于x的方程x²+2ax+b²＝0与x²-2cx-b²＝0有公共根的充要设a,b,c为△ABC的三边，求证：关于x的方程x²+2ax+b²＝0与x²-2cx-b²＝0有公共根的充要条
设a,b,c为△ABC的三边,求证：关于x的方程x²+2ax+b²＝0与x²-2cx-b²＝0有公共根的充要
设a,b,c为△ABC的三边，求证：关于x的方程x²+2ax+b²＝0与x²-2cx-b²＝0有公共根的充要条件是角A等于90°

设a,b,c为△ABC的三边,求证：关于x的方程x²+2ax+b²＝0与x²-2cx-b²＝0有公共根的充要设a,b,c为△ABC的三边，求证：关于x的方程x²+2ax+b²＝0与x²-2cx-b²＝0有公共根的充要条
充分性
因为A等于90°
所以b2+c2=a2代入x²+2ax+b²＝0与x²-2cx-b²＝0中得x²+2ax+ a2- c2＝0（x+a）2= c2
得到
x²-2cx-b²＝0得到x²-2cx- a2+ c2＝0得到（x-c）2= a2
得出公共根.
必要性
先解方程x²+2ax+b²＝0与x²-2cx-b²＝0得到x=(-b2)/(a+c),代入第一个方程求出勾股定理的式子

必要性：第一个方程减去第二个方程解得x=(-b^2)/(a+c)，代入第二个方程，整理化简立得b^2+c^2=a^2。
充分性：显然。

Work from home business success can be easily achieved when you know what it will take to make it happen. There are all kinds of people on the internet who have achieved the work from home business su...

全部展开

Work from home business success can be easily achieved when you know what it will take to make it happen. There are all kinds of people on the internet who have achieved the work from home business success that you are only dreaming about. There are some things that you need to do when you are trying to make your business a success. Let me explain what you will need to do. First,Christian Louboutin Tall Boots, you will need to educate yourself. You need to learn all you can about your new home business. You also need to learn how to market your business. People will not know you are there unless you can get your website in front of them. So learning how to market is one of the most important things that you will need to do. Second,Christian Louboutin Bridal Shoes, find a mentor that can you can learn from. When you find someone that has already achieved the success that you want it will make it much easier for you. There are all kinds of people out there that can be your mentor. They will be more than happy to show you how they got the success for their business. Now remember that it will take some time for you to make it to where they are but it can be done. Third,Christian Louboutin Heels, find a forum or any other place that people in other businesses or even the home business you are doing hang out. This will not only give you support when you have questions but you can also learn from what other people are doing to market their business. You will also be able to figure out what not to do by learning what others have tried and had no success with. Fourth,Christian Louboutin Flats, write down your goals. Many people never know how important this is. You can talk to anyone that has achieved success and every one of them will tell you that they wrote down their goals. This will help you see where you are going and will help to keep you on track. You will have to revise those goals every so often when you have achieved the first goals. These four things will help you find the work from home business success that you are looking for. It is a lot easier to do when you know what to do. The one major key to all of these four things is to learn. Education is very,Christian Louboutin Peep Toe, very important when you are trying to do anything that you are new to. Even if you are not new you can never have too much knowledge, especially with all of the new advertising methods that come up every day on the internet.

收起