Đáp án:
Bài 27:
G=(x+23x+2x+1−3):2−4xx+1+x2−3x−13x (x≠0;x≠−1;x≠12)
=(x+2)(x+1)+2.3x−3.3x(x+1)3x(x+1).x+12−4x+x2−3x+13x
=x2+3x+2+6x−9x2−9x3x.12−4x+x2−3x−13x
=−8x2+23x(2−4x)+x2−3x−13x
=−2(4x2−1)−3x(4x−2)+x2−3x−13x
=−2(2x−1)(2x+1)−3x.2(2x−1)+x2−3x−13x
=−2x−1−3x+x2−3x−13x
=−(2x+1)−3x+x2−3x−13x
=2x+13x+x2−3x−13x
=x2−3x−1+2x+13x=x2−x3x=x(x−1)3x=x−13
Vậy G=x−13 khi x≠0;x≠−1;x≠12