利用完全平方公式计算:2001²1.999²98²39²计算:(1)(2x+y)²-4xy(2)(x+2)(x-2)-(x-2)²(3)(m-n)²+(m+n)²(4) (2a+b)²-4(a+b)(a-2b)
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![利用完全平方公式计算:2001²1.999²98²39²计算:(1)(2x+y)²-4xy(2)(x+2)(x-2)-(x-2)²(3)(m-n)²+(m+n)²(4) (2a+b)²-4(a+b)(a-2b)](/uploads/image/z/14226242-50-2.jpg?t=%E5%88%A9%E7%94%A8%E5%AE%8C%E5%85%A8%E5%B9%B3%E6%96%B9%E5%85%AC%E5%BC%8F%E8%AE%A1%E7%AE%97%EF%BC%9A2001%26%23178%3B1.999%26%23178%3B98%26%23178%3B39%26%23178%3B%E8%AE%A1%E7%AE%97%EF%BC%9A%EF%BC%881%EF%BC%89%EF%BC%882x%2By%EF%BC%89%26%23178%3B-4xy%EF%BC%882%EF%BC%89%EF%BC%88x%2B2%29%EF%BC%88x-2%29-%EF%BC%88x-2%29%26%23178%3B%EF%BC%883%EF%BC%89%EF%BC%88m-n%29%26%23178%3B%2B%28m%2Bn%29%26%23178%3B%284%29+%282a%2Bb%29%26%23178%3B-4%28a%2Bb%29%28a-2b%29)
利用完全平方公式计算:2001²1.999²98²39²计算:(1)(2x+y)²-4xy(2)(x+2)(x-2)-(x-2)²(3)(m-n)²+(m+n)²(4) (2a+b)²-4(a+b)(a-2b)
利用完全平方公式计算:
2001²
1.999²
98²
39²
计算:
(1)(2x+y)²-4xy
(2)(x+2)(x-2)-(x-2)²
(3)(m-n)²+(m+n)²
(4) (2a+b)²-4(a+b)(a-2b)
利用完全平方公式计算:2001²1.999²98²39²计算:(1)(2x+y)²-4xy(2)(x+2)(x-2)-(x-2)²(3)(m-n)²+(m+n)²(4) (2a+b)²-4(a+b)(a-2b)
2001²
=(2000+1)²
=2000²+4000+1
=4000000+4000+1
=4004001
1.999²
=(2-0.001)²
=4-0.004+0.000001
=3.996001
98²
=(100-2)²
=10000-400+4
=9604
39²
=(40-1)²
=1600-80+1
=1521
计算:
(1)(2x+y)²-4xy
=4x²+4xy+y²-4xy
=4x²+y²
(2)(x+2)(x-2)-(x-2)²
=(x+2-x+2)(x-2)
=4x-8
(3)(m-n)²+(m+n)²
=m²-2mn+n²+m²+2mn+n²
=2m²+2n²
(4) (2a+b)²-4(a+b)(a-2b)
=4a²+4ab+b²-4(a²-ab-2b²)
=4a²+4ab+b²-4a²+4ab+8b²
=8ab+9b²