作业帮[（m^2+n^2)^2]-[(-m)^2-(-n)^2]^2的值?[（3a+2b)^2]-[(3a-2b)^2]的值?[2(x+y)(x-y)]-[(x+y)^2]-[(x-y)^2]的值?
来源：学生作业帮助网 编辑：作业帮 时间：2024/11/09 00:36:22
[（m^2+n^2)^2]-[(-m)^2-(-n)^2]^2的值?[（3a+2b)^2]-[(3a-2b)^2]的值?[2(x+y)(x-y)]-[(x+y)^2]-[(x-y)^2]的值?
[（m^2+n^2)^2]-[(-m)^2-(-n)^2]^2的值?
[（3a+2b)^2]-[(3a-2b)^2]的值?
[2(x+y)(x-y)]-[(x+y)^2]-[(x-y)^2]的值?
[（m^2+n^2)^2]-[(-m)^2-(-n)^2]^2的值?[（3a+2b)^2]-[(3a-2b)^2]的值?[2(x+y)(x-y)]-[(x+y)^2]-[(x-y)^2]的值?
[（m^2+n^2)^2]-[(-m)^2-(-n)^2]^2
=（m^2+n^2)^2-[m^2-n^2]^2
=(m^2+n^2+m^2-n^2)(m^2+n^2-m^2+n^2)
=2m^2*2n^2
=4m^2n^2
[（3a+2b)^2]-[(3a-2b)^2]
=2*3a*2*2b
=24ab
[2(x+y)(x-y)]-[(x+y)^2]-[(x-y)^2]
=(2x^2-2y^2)-(2x^2+2y^2)
=-4y^2
^啥意思
第一题：
[（m^2+n^2)^2]-[(-m)^2-(-n)^2]^2
=（m^2+n^2)^2-（m^2-n^2）^2
=(m^2+n^2+m^2-n^2)(m^2+n^2-m^2+n^2)
=4m^2n^2
第二题：
[（3a+2b)^2]-[(3a-2b)^2]
=[（3a+2b)+(3a-2b)]*[(3a+2b)-(...
全部展开
第一题：
[（m^2+n^2)^2]-[(-m)^2-(-n)^2]^2
=（m^2+n^2)^2-（m^2-n^2）^2
=(m^2+n^2+m^2-n^2)(m^2+n^2-m^2+n^2)
=4m^2n^2
第二题：
[（3a+2b)^2]-[(3a-2b)^2]
=[（3a+2b)+(3a-2b)]*[(3a+2b)-(3a-2b)]
=24ab
第三题：
将x+y看做a, x-y 看做b,等式变化为：
2ab-a^2-b^2
=-(a-b)^2
将a,b还原：
-[（x+y）-（x-y）]^2
=-4y^2
这三道题有一个共性，那就是将式子整体看为a、b，然后带入上式公式就可求的。第一、第二道体用了一个公式：a^2-b^2=(a+b)*(a-b)
收起