中二數學題兩條【求完整回答及解釋】

1. Let x be a^(-1) and y be b^(-1). Then the expression becomes

(x^2-y^2)/(x-y)=(x+y)=a^(-1)+b^(-1)=1/a+1/b

2. Laws of Indices:
(a^b)^c=a^(bc)
a^b/a^c=a^(b-c)
Using those above,
{3^[(-2)(2x+1)]-3^[3(1-x)]}/3^(4x)
=[3^(-4x-2)-3^(3-x)]/3^(4x)
=3^(-8x-2)-3^(3-5x)