- (1) x2-49y2; (2) 0.04x2-0.09; (3) m2n2-9n2;
(4) 4x2-9y2; (5) 1/16x2-4y2; (6) n2-25m2. - (1) 4m2-9; (2) x+4; (3) 9x2+xy; (4) -8a2+15/4b2.
- (1) 4x2+20xy+25y2; (2) 1/9m2-1/3m+1/4;
(3) 4t2+4t+1; (4) 1/25x2+1/25xy+1/100y2;
(5) 49a2b2+28ab+4; (6) c2d2-cd+1/4. - (4πr-4π) cm2.
- (1) 4x2+4xy+y2-1; (2) 2x-1;
(3) 4ab; (4) -8xy+9y2. - (1) 999 951; (2) 12 096.
- 它的体积增加了 (6a2+60a) cm3.
- (1) 3 969; (2) 996 004.
- 略。
- (1) a2n-b2; (2) a4-1.
- 末尾的两个数为 25.
设个位数是 5 的两位数为 10a+5, 则 (10a+5)2=100a2+100a+25, 由此可知个位数字是 5 的两位数平方后, 末尾的两个数是 25.
类似规律略。 - a3+3a2b+3ab2+b3.
- ※a2+b2+c2+2ab+2bc+2ac.
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