... Q(x)=P(x)-x 2 ⇒Q (1 )= Q(2)=Q(3)=Q(4)=Q(5)=0. ⇒Q(x) có 5 nghiệm 1,2,3,4,5 Q(x)=(x -1 )( x-2)(x-3)(x-4)(x-5) ⇒P(x)= (x -1 )( x-2)(x-3)(x-4)(x-5)+x 2 ⇒P(6)=5.4.3.2.1+6 2 =156;P(7)=6.5.4.3.2+7 2 =769 P(6)=156 ... + . Biết P (1 )= 1, P(2)=4, P(3) =9, P(4)=16, P(5)=25. Tính P(6), P(7). Bài 7: Cho đa thức: 2 2 2 2 2 1 1 1 1 1 P(x) x x x 3x 2 x 5x 6 x 7x 12 x 9x 20 = + + + + + + + + + + + + + Tính P(0,9). Bài ... ⇒P(6)=5.4.3.2.1+6 2 =156;P(7)=6.5.4.3.2+7 2 =769 P(6)=156 P(7)=769 0,5đ 0,5đ 7 1 1 1 P(x) x(x 1) (x 1 )( x 2) (x 2)(x 3) 1 1 1 1 (x 3)(x 4) (x 4)(x 5) x x 5 = + + + + + + + + + = − + + + + + =0,94161...