做得好+++分1:x^2-7X+122:X^2+7X+103:(X+Y除4X+21)X+Y-------4X+214:(X^2-4除X^2+3X+2)X^2-4-------X^2+3X+2能说一下用什么方法做吗?3.是:(X+7除4X+28)

问题描述:

做得好+++分
1:x^2-7X+12
2:X^2+7X+10
3:(X+Y除4X+21)
X+Y
-------
4X+21
4:(X^2-4除X^2+3X+2)
X^2-4
-------
X^2+3X+2
能说一下用什么方法做吗?3.是:(X+7除4X+28)

1.(x-3)(x-4)
2.(x+2)(x+5)
3.没看懂题目
4.分子为(x+2)(x-2)
分母为(x+1)(x+2)
约分 得 (x-2)/(x+1)且x≠-2
一定要注明x≠-2

1:x^2-7X+12=(x-3)(x-4)
2:X^2+7X+10=(x+2)(x+5)
3:(X+Y除4X+21)
X+Y X+Y
------- = --------
4X+21 4X+21
4:(X^2-4除X^2+3X+2)
X^2-4 (x-2)(x+2) x-2
------- =-------------=--------
X^2+3X+2 (+1)(x+2) x+1

1:x^2-7X+12=(x-3)(x-4)
2:X^2+7X+10=(x+2)(x+5)
3:(X+Y)/(4X+21)
这题是不是错了啊?
4:(X^2-4)/(X^2+3X+2)=[(x+2)(x-2)]/[(x+1)(x+2)]
=(x-2)/(x+1)

1:x^2-7X+12
这是用十字配方法
1 -4
1 -3
=(x-4)(x-3)
2:X^2+7X+10
=(x+5)(x+2)
1 5
1 2
3:X+7除4X+28
X+7
-------
4X+28
=(x+7)/4(x+7)
=1/4
4:(X^2-4除X^2+3X+2)
X^2-4
-------
X^2+3X+2
=(x+2)(x-2)/(x+2)(x+1)
=(x-2)/(x+1)