(1) It is known that | m- 1 |+(m-n+ 1) 2 = 0 and | m-1| > = 0, (m-n+1) 2> =0,

So M= 1, M-N+ 1=0, that is, m = 1, n = 2 are arranged in descending order by the letter X as follows.

-2x^3+0.4x^2- 1/3*x^2+ 1

(2) It is known that the polynomial is cubic, and the polynomial given in the title is four terms, so one term must be zero, so M=2, and all the coefficients except 0.5xy (2n+6) * z 3 are less than 6, so 1+(2N+6)+3=6, and N=-2 is obtained.

(3) From the meaning of the question, 2m-8pi = 0,1+n+1+1= 2+3+3, so M=4Pi, N=5.

(π is π)

(4) Arranged in ascending order of X letters.

(5)-x+7,a+b^2,a/3+b,5x^3*y^2-3x^2*y^3，

8a 2-3ab is a polynomial.

-0.6a 2 * b,-1 1 is a monomial.