三道平方差公式题应用平方差解下列各题题目在此:http://i336.photobucket.com/albums/n351/Creattive/123112322.jpg
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三道平方差公式题应用平方差解下列各题题目在此:http://i336.photobucket.com/albums/n351/Creattive/123112322.jpg
三道平方差公式题
应用平方差解下列各题
题目在此:http://i336.photobucket.com/albums/n351/Creattive/123112322.jpg
三道平方差公式题应用平方差解下列各题题目在此:http://i336.photobucket.com/albums/n351/Creattive/123112322.jpg
1、(3+1)(3^2+1)(3^4+1)(3^8+1)...(3^(2^n)+1)
=(3-1)(3+1)(3^2+1)(3^4+1)(3^8+1)...(3^(2^n)+1)/2
=(3^2-1)(3^2+1)(3^4+1)(3^8+1)...(3^(2^n)+1)/2
=(3^4-1)(3^4+1)(3^8+1)...(3^(2^n)+1)/2
..
..
..
=(3^(2^(n+1))-1)/2
2、(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)(1+1/2^15)
=2(1-1/2)(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)(1+1/2^15)
=2(1-1/2^2)(1+1/2^2)(1+1/2^4)(1+1/2^8)(1+1/2^15)
=2(1-1/2^4)(1+1/2^4)(1+1/2^8)(1+1/2^15)
=2(1-1/2^8)(1+1/2^8)(1+1/2^15)
=(2-1/2^15)(1+1/2^15)=(1+1-1/2^15)(1+1/2^15)
=1+1/2^15+1-1/2^30=2+1/2^15-1/2^30
3、4x^2-9y^2=31
(2x+3y)(2x-3y)=1*31
2x+3y=31
2x-3y=1
解得:x=8;y=5