2.已知a+b=2 ,求(a²-b²)²-8(a²+b²)的值
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![2.已知a+b=2 ,求(a²-b²)²-8(a²+b²)的值](/uploads/image/z/3691046-38-6.jpg?t=2.%E5%B7%B2%E7%9F%A5a%2Bb%3D2+%2C%E6%B1%82%EF%BC%88a%26%23178%3B-b%26%23178%3B%29%26%23178%3B-8%EF%BC%88a%26%23178%3B%2Bb%26%23178%3B%EF%BC%89%E7%9A%84%E5%80%BC)
2.已知a+b=2 ,求(a²-b²)²-8(a²+b²)的值
2.已知a+b=2 ,求(a²-b²)²-8(a²+b²)的值
2.已知a+b=2 ,求(a²-b²)²-8(a²+b²)的值
(a²-b²)²-8(a²+b²)
=[(a+b)(a-b)]²-8(a²+b²)
=(a+b)²(a-b)²-8(a²+b²) a+b用2代替
=4(a-b)²-8(a²+b²)
=4a²-8ab+4b²-8a²-8b²
=-4a²-8ab-4b²
=-4(a²+2ab+b²)
=-4(a+b)²
=-16