`c)` `C = ((xsqrtx+1)/(x-1)-(x-1)/(sqrtx-1))\div(sqrtx+sqrtx/(sqrtx-1)`
`= (((sqrtx+1)(x-sqrtx+1))/((sqrtx-1)(sqrtx+1))-(x-1)/(sqrtx-1)) \div ((sqrtx-1)sqrtx+sqrtx)/(sqrtx-1)`
`= ((x-sqrtx+1)/(sqrtx-1) - (x-1)/(sqrtx-1)) \div (x-sqrtx+sqrtx)/(sqrtx-1)`
`= (x-sqrtx+1-(x-1))/(sqrtx-1) * (sqrtx-1)/x`
`= (x-sqrtx+1-x+1) * 1/x`
`= (-sqrtx+2)*1/x`
`= (-(sqrtx+2))/x`
`d)` `D = ((a+2)/(asqrta-1)+(sqrta)/(a+sqrta+1)+1/(1-sqrta))\div(sqrta-1)/2`
`= ((a+2)/((sqrta-1)(a+sqrta+1)) + sqrta/(a+sqrta+1)-1/(sqrta-1))*2/(sqrta-1)`
`= (a+2+(sqrta-1)sqrta-(a+sqrta+1))/((sqrta-1)(a+sqrta+1)) * 2/(sqrta-1)`
`= (a+2+a-sqrta-a-sqrta-1)/((sqrta-1)(a+sqrta+1)) * 2/(sqrta-1)`
`= (1^2-2*1*sqrta+sqrta^2)/((sqrta-1)(a+sqrta+1)) * 2/(sqrta-1)`
`= ((-(sqrta-1))^2)/((sqrta-1)(a+sqrta+1)) * 2/(sqrta-1)`
`= ((sqrta-1)^2)/((sqrta-1)(a+sqrta+1)) * 2/(sqrta-1)`
`= 1/(a+sqrta+1) * 2`
`= 2/(a+sqrta+1)`
