✔ 最佳答案
x 3x+5
---------- + ------------
5-x x^2-25
The thing is that you should see that x^2-25 us x*x and 5*5. x^2-25 is the same as (x+5)(x-5)
x 3x+5
---------- + --------------
5-x (x+5)(x-5)
Next thing is to spot 5-x needs to be in the right form. So we put the - outside (- = -1 actually) -(x-5). The order of the terms in the paramter doesn't matter since both are poistive now. Before they actually were (+5-x), but now with the - outside we get a similar form as the stuff on the right.
x 3x+5
---------- + --------------
-(x-5) (x+5)(x-5)
So - now that we can see what unifies them we can multiply the different blocks with what they lack. Left block needs to be multiplied with (x+5), and the right block needs to be multiplied with -1.
So - what we do on the blocks must happen both on the upper number and lower number.
x 3x+5
---------- + --------------
-(x-5) (x+5)(x-5)
x(x+5) + -(3x+5)
----------------------------------
-(x-5)(x+5) + -(x+5)(x-5)
x^2+5x+(-3x-5)
---------------------
-(x+5)(x-5)
And the final calculations give;
x^2+2x-5
----------------
-(x+5)(x-5)
參考: I hate yahoo for removing my extra spaces. This is unreadable you twats!