Đáp án:
`a)``P=1/(\sqrtx -4)`
`b)`` x=(81)/4`
Giải thích các bước giải:
`a) ĐKXĐ: x>=0,x\ne9,x\ne16`
`P= (2\sqrtx +3)/(\sqrtx -3) +(\sqrtx +3)/(4-\sqrtx )-(x-6\sqrtx )/[(\sqrtx -3)(\sqrtx -4)]`
`P=(2\sqrtx +3)/(\sqrtx -3) -(\sqrtx +3)/(\sqrtx -4)-(x-6\sqrtx )/[(\sqrtx -3)(\sqrtx -4)]`
`P=[(2\sqrtx +3)(\sqrtx -4) -(\sqrtx +3)(\sqrtx -3)-x+6\sqrtx]/[(\sqrtx -3)(\sqrtx -4)]`
`P=(2x -8\sqrtx+3\sqrtx -12-x+9-x+6\sqrtx)/[(\sqrtx -3)(\sqrtx -4)]`
`P=(\sqrtx -3)/[(\sqrtx -3)(\sqrtx -4)]`
`P=1/(\sqrtx -4)`
Vậy `P=1/(\sqrtx -4) với x>=0,x\ne9,x\ne16`
`b)` Để `P=2`
`<=>1/(\sqrtx -4)=2 ( đk: x>=0,x\ne9,x\ne16)`
`=> 2\sqrtx -8=1`
`<=>2\sqrtx =9`
`<=>\sqrtx=9/2`
`<=>x=(81)/4`(t/m)
Vậy `x=(81)/4` thì `P=2`
