M = x^2 + 5x^4 − 3x^3 + x^2 + 4x^4 + 3x^3 − x + 5
M = (x^2+ x^2)+(5x^4 + 4x^4)+(− 3x^3+ 3x^3)− x + 5
M = 2x^2 + 9x^4 - x +5
M = 9x^4+2x^2 - x +5
N = x − 5x^3 − 2x^2 − 8x^4 + 4 x^3 − x + 5
N = (x-x)+(− 5x^3 + 4 x^3) − 2x^2− 8x^4+ 5
N = -x^3 - 2x^2− 8x^4+ 5
N = − 8x^4-x^3- 2x^2+ 5
M+N=(9x^4+2x^2 - x +5)+(− 8x^4-x^3- 2x^2+ 5)
M+N=9x^4+2x^2 - x +5− 8x^4-x^3- 2x^2+ 5
M+N=(9x^4− 8x^4)+(2x^2- 2x^2)+(5+5)-x^3x-x
M+N= x^4+10-x^3x-x
M - N=(9x^4+2x^2 - x +5)-(− 8x^4-x^3- 2x^2+ 5)
M - N=9x^4+2x^2 - x +5+8x^4+x^3+2x^2-5
M - N=(9x^4+8x^4)+(2x^2+2x^2)+(5-5) - x +x^3
M - N= 17x^4+4x^2-x+x^3
xin hay nhất ạ