m- 1= 12
m= 1 12
M=- 1 1 or m= 13.
12、x? +y? =(x+y)? -2xy=5? -2*3= 19
3x? +3y? =3* 19=57
13 、( a+3)? +|b-3|=0
a+3=0
a=-3
b-3=0
b=3
a-b=-3-3=-6
14、x? -(y+z)? =6
(x+y+z)(x-y-z)=6
2(x-y-z)=6
x-y-z=3
15、n? -n? -n+5=n(n? -n- 1)+5=n*0+5=5