1 7*3^4+8*3^3-(-13)*3^2 = 900
2 202^2-54^2+256*352 = 128 000
3 3.21*91+156*3.21-3.21*147 = 321
4.原式=(a-1)×原式/(a-1)=(a^2-1)( a^2+1)(a^4+1)(a^8+1)……(a^128+1)/(a-1)
=( a^4-1)(a^4+1)(a^8+1)……(a^128+1)/(a-1)
=(a^8-1)(a^8+1)……(a^128+1)/(a-1)
=(a^128-1) (a^128+1)/(a-1)
=(a^256-1)/ (a-1) +1