（2mn+1)(2mn-1)-(2m²n²+2)怎么算啊?

（2mn+1)(2mn-1)-(2m²n²+2)怎么算啊?
（2mn+1)(2mn-1)-(2m²n²+2)怎么算啊?

（2mn+1)(2mn-1)-(2m²n²+2)怎么算啊?
3a^m-1 bc^2和-2a^3 b^n-2 c^2是同类项
m-1=3,1=n-2
m=4,n=3
3m^2 n-2mn^2+2m^2 n+4mn^2-mn
=5m^2n+2mn^2-mn
=mn(5m+2n-1)
=4*3*(5*4+2*3-1)
=12*25
=300

a=m^2+n^2
b=m^2-n^2
c=2mn
b^+c^2=(m^2-n^2)^2+(2mn)^2
=m^4-2m^2*n^2+n^4+4m^2*n^2
=m^4+2m^2*n^2+n^4=(m^2+n^2)=a^2
即：b^2+c^2=a^2
所以，m^2+n^2,m^2-n^2,2mn这三个数就是一组勾股数组。

39/4m^2 n^6 -1/3mn^4

1,这个你把他们的值代进去就可以了，我没时间了，给你解第二道啊。
2.4(-2mn+2m+3n)-2(3m+5n-mn)
=-8mn+8m+12n-6m-10n+2mn
=-6mn+2m+2n
=-6mn+2(m+n)
=-6*(-1)+2*3
=6+6
=12

m^2-mn=21..................1
mn-n^2=-15...............2
1式+2式得
m^2-n^2=6
1式-2式得
m^2-2mn+n^2=21-(-15)=36

m=1,n=±1
2m²n＋2mn－3nm²－3nm＋4m²n
=mn(2m＋2－3m－3＋4m)
=mn(3m－1)
=±2

是要因式分解吗？
(1)=x(x^4-1)=x(x^2＋1)(x^2-1)=x(x^2＋1)(x＋1)(x-1)
(2)=(m-n)^2-2(m-n)＋1=(m-n-1)^2
(3)=(x^2＋4)^2-(4x)^2=(x^2＋4＋4x)(x^2＋4-4x)=[(x＋2)(x-2)]^2