Because n is greater than 0, M=36 and N=6, M-N=36-6=30.
Question 2: How to judge whether this equation is a quadratic equation? It is found that the coefficient of quadratic term is not 0. Answer? -8a+20=a？ -8a+ 16+4=(a-4)？ +4. Because (a-4)? Is a non-negative number, plus four is a positive number, so it must be a quadratic equation.
Question 3: X? +2(√2- 1)x + 3 - 2√2=0
x？ +2(√2- 1)x =2√2-3
x？ +2(√2- 1)x+2-2√2+ 1 = 2√2-3+2-2√2+ 1
(x+√2- 1)？ =0
(x+√2- 1)=0
X= 1-√2