`1.16`

`P=( (1-a\sqrt{a})/(1-\sqrt{a}) + \sqrt{a} )( (1-\sqrt{a})/(1-a) )^2`

   `= (1-a\sqrt{a}+\sqrt{a}-a)/(1-\sqrt{a}) . ( (1-\sqrt{a})/( (1-\sqrt{a})(1+\sqrt{a}) ) )^2`

   `= ( (1+\sqrt{a})-(a+a\sqrt{a}) )/(1-\sqrt{a}) . ( 1/(1+\sqrt{a}) )^2`

   `= ( (1+\sqrt{a})-a(\sqrt{a}+1) )/(1-\sqrt{a}) . 1/( (1+\sqrt{a})^2 )`

   `= ( (1+\sqrt{a})(1-a) )/(1-\sqrt{a}) . 1/( (1+\sqrt{a})^2 )`

   `= ( (1-\sqrt{a})(1+\sqrt{a}) )/(1-\sqrt{a}) . 1/(1+\sqrt{a})`

   `= 1`

Vậy `P= 1`

`1.17`

`P=( (\sqrt{a})/2 - 1/(2\sqrt{a}) )( (\sqrt{a}-1)/(\sqrt{a}+1) - (\sqrt{a}+1)/(\sqrt{a}-1) )`

   `=( a-1 )/( 2\sqrt{a} ) . ( (\sqrt{a}-1)^2 - (\sqrt{a}+1)^2 )/( (\sqrt{a}+1)(\sqrt{a}-1) )`

   `= (a-1)/(2\sqrt{a}) . (a-2\sqrt{a}+1-a-2\sqrt{a}-1)/(a-1)`

   `= (a-1)/(2\sqrt{a}) . (-4\sqrt{a})/(a-1)`

   `= -2`

Vậy `P=-2`

`1.18`

`P=(\sqrt{x})/(\sqrt{x}+3) + 3/(\sqrt{x}-3) +(x+9)/(9-x)`

   `= ( \sqrt{x}(\sqrt{x}-3)+3(\sqrt{x}+3) )/( (\sqrt{x}+3)(\sqrt{x}-3) ) - (x+9)/(x-9)`

   `= ( x-3\sqrt{x}+3\sqrt{x}+ 9)/(x-9) - (x+9)/(x-9)`

   `= ( x+9)/(x-9) - (x+9)/(x-9)`

   `=0`

Vậy `P=0`

`#` `ccUh`