已知实数a,b满足a+b=7,ab=12,求下列代数式的值(1) (a-b)² (2)a²-ab+b² (3)(a²+1)(b²+1) 和 乘法公式
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![已知实数a,b满足a+b=7,ab=12,求下列代数式的值(1) (a-b)² (2)a²-ab+b² (3)(a²+1)(b²+1) 和 乘法公式](/uploads/image/z/5543577-9-7.jpg?t=%E5%B7%B2%E7%9F%A5%E5%AE%9E%E6%95%B0a%2Cb%E6%BB%A1%E8%B6%B3a%2Bb%3D7%2Cab%3D12%2C%E6%B1%82%E4%B8%8B%E5%88%97%E4%BB%A3%E6%95%B0%E5%BC%8F%E7%9A%84%E5%80%BC%281%29+%28a-b%29%26%23178%3B+%EF%BC%882%EF%BC%89a%26%23178%3B-ab%2Bb%26%23178%3B+%EF%BC%883%EF%BC%89%EF%BC%88a%26%23178%3B%2B1%EF%BC%89%EF%BC%88b%26%23178%3B%2B1%EF%BC%89+%E5%92%8C+%E4%B9%98%E6%B3%95%E5%85%AC%E5%BC%8F)
已知实数a,b满足a+b=7,ab=12,求下列代数式的值(1) (a-b)² (2)a²-ab+b² (3)(a²+1)(b²+1) 和 乘法公式
已知实数a,b满足a+b=7,ab=12,求下列代数式的值
(1) (a-b)² (2)a²-ab+b² (3)(a²+1)(b²+1) 和 乘法公式
已知实数a,b满足a+b=7,ab=12,求下列代数式的值(1) (a-b)² (2)a²-ab+b² (3)(a²+1)(b²+1) 和 乘法公式
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~
(1)(a-b)²=(a+b)²-4ab=49-48=1
(2)a²+b²-ab=(a+b)²-3ab=49-36=13
(3)(a²+1)(b²+1)=(ab)²+a²+b²+1=144+(a+b)²-2ab+1=144+49-24+1=170
1、
(a-b)²
=a²+b²-2ab
=a²+b²+2ab-4ab
=(a+b)²-4ab
=7²-4*12
=1
2、
a²-ab+b²
=a²+b²+2ab-3ab
=(a+b)²-3ab
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1、
(a-b)²
=a²+b²-2ab
=a²+b²+2ab-4ab
=(a+b)²-4ab
=7²-4*12
=1
2、
a²-ab+b²
=a²+b²+2ab-3ab
=(a+b)²-3ab
=7²-3*12
=13
3、
(a²+1)(b²+1)
=a²b²+a²+b²+1
=(ab)²+(a+b)²-2ab+1
=12²+7²-2*12+1
=144+49-24+1
=170
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(1)
﹙a-b﹚²=﹙a+b﹚²-4ab
=49-48
=1
(2)
a²-ab+b²=a²-ab+b²+2ab-2ab
=﹙a+b﹚²-3ab...
全部展开
(1)
﹙a-b﹚²=﹙a+b﹚²-4ab
=49-48
=1
(2)
a²-ab+b²=a²-ab+b²+2ab-2ab
=﹙a+b﹚²-3ab
=49-36
=13
(3)
﹙a²+1﹚﹙b²+1﹚=a²b²+a²+b²+1
=a²b²+a²+b²+1+2ab-2ab
=﹙a+b﹚²+a²b²+1-2ab
=49+144+1-24
=170;
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