(-2)-1=(-1)…12-1 7.证明: 2 b2b=(a-b)3 b2 +6 26 6 a+6-26 26 (-1)3 (a-b)2 (a-b)3 11 a2(a+1)2(a+2)2(a+3) b2(b+1)2(b+2)2(b+3)2 (2) c2(c+1)2(c+2)2(c+3)2 十 1a2+4a+4a2+9a+9 证:等式左嶝。|b2b2+2b+1b+4b+4b2+9b+9 2c2+2c+1c2+4c+4c2+9+9 a2+4d+4d+9d+9 a22a+14a+49a+9 c+(-1)cb22b+14b+49b+9 8:{-8|2+14 d 9 2a+1 b22b+1b+1b+1 1c+1 d22d+1d+1d+1