... x3-3x-2 = x3-2x-2 = x(x2-1)-2(x+1)=x(x+1)(x-1)-2(x+1)=(x+1)(x2-x-2)=(x+1 )(+ 1)(x-2) = (x+1)2(x-2)MTC ở 2 vế (x+1)2(x-2) 2 22 25 ( 1) ( 2) ( 1) ( 2) ( 1) ( 2)x a x b xx x x x+ ... đổi thành x2+x-56=0 (x-7)(x +8) =0kq S = {7 ; -8} c.x2-3x+2 =(x-1)(x-2)x2-4x+3 =(x-1)(x-3)đkxđ : x1, x2, x34 1 2 5 ( 1 )( 2) ( 1 )( 3) ( 1 )( 3)4 4 ( 1 )( 2) ( 1 )( 3)x x xx x x x x xx ... a>0f(x)<-ab.f(x) >g(x) f(x) <-g(x)f(x)<g(x)Dạng 3.f(x) >g(x) [f(x)]2>[g(x)]2hay là [f(x)-g(x)][f(x)+g(x)]>02. CM 22x yxyổ ử+ữỗữỗữữỗố ứ (1 )C1....