Question

这几道题怎么写呀，求解！

就是前面这六道小题

Answer 1

如下

Answer 2

（6）y =[(x^2+1)-1] / (x^2+1) 

= √(x^2+1) - 1/√(x^2+1) 

= (x^2+1)^(1/2) - (x^2+1)^(-1/2)

y ' = 1/2 * (x^2+1)^(-1/2) * 2x + 1/2*(x^2+1)^(-3/2) * 2x

= x(x^2+1)^(-1/2) + x(x^2+1)^(-3/2)

y ' ' = (x^2+1)^(-1/2) + x*(-1/2)*(x^2+1)^(-3/2)*2x

+ (x^2+1)^(-3/2) + x*(-3/2)*(x^2+1)^(-5/2) * 2x

=(x^2+1)^(-1/2) + (1-x^2)(x^2+1)^(-3/2) - 3x^2*(x^2+1)^(-5/2)