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(5a+3b)(3a-5b)-(3a+b)(-b+3a)

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(5a+3b)(3a-5b)-(3a+b)(-b+3a)
计算:(附详细讲解(分析)、答案.)
1.(5a+3b)(3a-5b)-(3a+b)(-b+3a)
2.(1-1/2²)(1-1/3²)(1-1/4²)……(1-1/2013²)
3.已知m-n=4,m^2-n^2=24,求(m+n)^2
(5a+3b)(3a-5b)-(3a+b)(-b+3a)
/>(5a+3b)(3a-5b)-(3a+b)(-b+3a)
 =15a^2-16ab-15b^2-(9a^2-b^2)
=15a^2-16ab-15b^2-9a^2+b^2
=7a^2-16ab-13b^2

 
2.(1-1/2²)(1-1/3²)(1-1/4²)……(1-1/2013²)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)……(1-1/2013)(1+1/2013)
=1/2*3/2*2/3*4/3*3/4*5/4*……*2012/2013*2014/2013
=1/2*2014/2013
=1007/2013

 3.已知m-n=4,m^2-n^2=24,求(m+n)^2
m^2-n^2=(m-n)(m+n)=24     m-n=4
m+n=6
(m+n)^2=36