1.(2+1)(2^2+1)……(2^2048+1)
=(2-1)(2+1)(2^2+1)……(2^2048+1)/(2-1)
=(2^2-1)(2^2+1)(2^4+1)……(2^2048+1)
=……
=2^4096-1
2.(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15
=(1-1/2)(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)/(1-1/2)+1/2^15
=……
=(1-1/2^16)/(1/2)+1/2^15
=2-1/2^15+1/2^15
=2
3^x=2
（x/9）²-1=x^2/9^2 -1=4/81 -1=-77/81
應該是(x/9)^2-1吧?
x-y=1,
x^2-y^2+3x-5y=(x+y)(x-y)+3x-5y=x+y+3x-5y=4x-4y=4(x-y)=4