解:原式=(a-3b)^2+(3a+b)^2-(a+5b)^2+(a-5b)^2
=a^2-6ab+9b^2+9a^2+b^2+6ab-a^2-10ab-25b^2+a^2-10ab+25b^2
=(1+9-1+1)a^2+(-6+6-10-10)ab+(9+1-25+25)b^2
=10a^2-20ab+10b^2
=10(a^2-2ab+b^2)
=10(a+b)^2
=10*(-8-6)^2
=1960
解:原式=2^(n+4)-2^n
=2^n*(2^4-1)
=2^n*15
=15*2^n
得证