您好:
1) (a-b)²
=(a+b)² -4ab
=7² -4x12
=1
(2)a²-ab+b²
=(a+b)² -3ab
=7² -3x12
=49-36
=13
(3)(a²+1)(b²+1)
=a² b² +a² +b² +1
=(ab)² +(a+b)² -2ab+1
=12² +7² -2x12+1
=144+49-24+1
请好评~
您好:
1) (a-b)²
=(a+b)² -4ab
=7² -4x12
=1
(2)a²-ab+b²
=(a+b)² -3ab
=7² -3x12
=49-36
=13
(3)(a²+1)(b²+1)
=a² b² +a² +b² +1
=(ab)² +(a+b)² -2ab+1
=12² +7² -2x12+1
=144+49-24+1
请好评~