Đáp án:
Giải thích các bước giải:
b) 1/(x-2)(x-3) + 1/(x-3)(x-4) + 1/(x-4)(x-5)
<=> ( x- 4 ) ( x- 5 ) + ( x - 2 ) ( x- 5 ) + ( x- 2 ) ( x- 3 ) / ( x - 2 ) ( x - 3 ) ( x - 4 ) ( x- 5 )
<=> x^2 - 5x - 4x + 20 + x^2 - 5x - 2x + 10 + x^2 -3x - 2x + 6 / ( x - 2 ) ( x - 3 ) ( x - 4 ) ( x- 5 )
<=> 3x^2 - 21x + 36 / ( x - 2 ) ( x - 3 ) ( x - 4 ) ( x- 5 )
<=> 3 ( x^2 - 7x + 12 ) / ( x - 2 ) ( x - 3 ) ( x - 4 ) ( x- 5 )
<=> 3 ( x^2 - 3x - 4x + 12 ) / ( x - 2 ) ( x - 3 ) ( x - 4 ) ( x- 5 )
<=> 3 [ x ( x - 3 ) - 4 ( x - 3 ) ] / ( x - 2 ) ( x - 3 ) ( x - 4 ) ( x- 5 )
<=> 3 ( x - 3 ) ( x- 4 ) / ( x - 2 ) ( x - 3 ) ( x - 4 ) ( x- 5 )
<=> 3 / ( x- 2 ) ( x- 5 )
<=> 3 / x^2 - 5x - 2x + 10
<=> 3 / x^2 - 7x + 10
