Two 1-+
2 ( 1) n- 1,n,n+ 1 (2) 2n-4,2n-2,2n
3 -2b 4 5 27 6 89
three
1 、( 1)3( 1-2ab 2)-2(a2 b-4ab 2)(2)x-(3x-2)+(2x-3);
Solution: Original formula =3-6ab2-2a2b+8ab2 Solution: Original formula = x-3x+2+2x-3.
=3-6ab2+8ab2-2a2b = x-3x+2x+2-3
= 3+(-6ab 2+8ab 2)-2a2b =(x-3x+2x)+(2-3)
=3+2ab2-2a2b = - 1
(3) 3a2-2(2a2+a)+2(a2-3a), where a =-2;
Solution: Original formula =3a2-4a2-2a+2a2-6a
=3a2-4a2+2a2-2a-6a
=(3a2-4a2+2a2)+(-2a-6a)
= a2-8a
Substituting a=-2, the original formula is =(-2)2-8×(-2).
= 4+ 16
= 20
2. Nitrogen
3、 10y+x 10x+y