[x的平方-16除以x平方+8x+16]+x除以x-4
=(x+4)(x-4)/(x+4)^2+x/(x-4)
=(x-4)/(x+4)+x/(x-4)
=[(x-4)^2+x(x+4)]/(x+4)(x-4)
=(x^2-8x+16+x^2+4x)/(x+4)(x-4)
=(2x^2-4x+16)/(x+4)(x-4)
=2(x^2-2x+8)/(x+4)(x-4)