Câu hỏi của Nguyễn Phong

Question

Cho các đa thức:

M=5x4-4x3-3x2-2x+4

N=x4-3x2+5x-7

P=-2x4-5x3+2x2-x-9.Tính:

a)M+N-P   b)M-N+P  c)N-M-P

Bro_Jeon_Downy · Accepted Answer

a) M+N-P= (5x4-4x3-3x2-2x+4)+(x4-3x2+5x-7)-(-2x4-5x3+2x2-x-9)

=5x4-4x3-3x2-2x+4+x4-3x2+5x-7-2x4+5x3-2x2+x+9

=5x4+x4-2x4-4x3+5x3-3x2-3x2-2x2-2x+5x+x+4-7+9

=4x4+x3-8x2+4x+6

b) M-N+P=(5x4-4x3-3x2-2x+4)-(x4-3x2+5x-7)+(-2x4-5x3+2x2-x-9)

=5x4-4x3-3x2-2x+4-x4+3x2-5x+7+-2x4-5x3+2x2-x-9

=5x4-x4-2x4-4x3-5x3-3x2+3x2+2x2-2x-5x-x+4+7-9

=2x4-9x3+2x2-8x+2

c)N-M-P=(x4-3x2+5x-7)-(5x4-4x3-3x2-2x+4)-(-2x4-5x3+2x2-x-9)

=x4-3x2+5x-7-5x4+4x3+3x2+2x-4-2x4+5x3-2x2+x+9

=x4-5x4-2x4+4x3+5x3-3x2+3x2-2x2+5x+2x+x-7-4+9

=-6x4+9x3-2x2+8x-2

Bạn xem lại thử đúng không nha, mình làm có gì sai sót thì bạn nói mình để mình rút kinh nghiệm.Câu trả lời: a) M+N-P= (5x4-4x3-3x2-2x+4)+(x4-3x2+5x-7)-(-2x4-5x3+2x2-x-9)