已知4m+n=90,2m-3n=10,求(m+2n)^2-(3m-n)^2的值
问题描述：
已知4m+n=90,2m-3n=10,求(m+2n)^2-(3m-n)^2的值
(m+n)^2-n^2
4a^2-(b+c)^2
169(a-b)^2-196(a+b)^2
(a+b+c)^2-(a+b-c)^2
4(2p+3q)^2-(3p-q)^2
1-a^4
2ab^3-2ab
3a-3ay^4
(2x+1)(x-1)-(x+1)(x-2)-10
答
(m+2n)^2-(3m-n)^2=(m+2n+3m-n)(m+2n-3m+n)=(4m+n)(-2m+3n)=-(4m+n)(2m-3n)=-90×10=-900(m+n)^2-n^2=(m+n+n)(m+n-n)=m(m+2n)4a^2-(b+c)^2=(2a+b+c)(2a-b-c)169(a-b)^2-196(a+b)^2=(13a-13b+14a+14b)(13a-13b-14a-14...