`a,M=\sqrt{75}-\sqrt{12}-\sqrt{48}+\sqrt{3}`
`=5\sqrt{3}-2\sqrt{3}-4\sqrt{3}+\sqrt{3}`
`=0`
Vậy `M=0`
`b,N=3\sqrt{3}-7\sqrt{27}+2\sqrt{243}`
`=3\sqrt{3}-21\sqrt{3}+18\sqrt{3}`
`=0`
Vậy `N=0`
`c,ĐKXĐ:x\ge0,x\ne1`
`P={x-2}/{\sqrt{x}-1}+{x}/{\sqrt{x}+1}`
`={(x-2)(\sqrt{x}+1)}/{(\sqrt{x}+1)(\sqrt{x}-1)}+{x(\sqrt{x}-1)}/{(\sqrt{x}+1)(\sqrt{x}-1)}`
`={(x-2)(\sqrt{x}+1)+x(\sqrt{x}-1)}/{(\sqrt{x}+1)(\sqrt{x}-1)}`
`={x\sqrt{x}+x-2\sqrt{x}-2+x\sqrt{x}-x}/{x-1}`
`={2x\sqrt{x}-2\sqrt{x}-2}/{x-1}`
`={2x\sqrt{x}-2\sqrt{x}-2}/{x-1}`
`x=4(TM)`
Thay `x=4` vào `P` có:
`P={2.4\sqrt{4}-2\sqrt{4}-2}/{4-1}`
`={8.2-2.2-2}/{3}`
`={16-4-2}/{3}`
`={10}/{3}`
Vậy với `x=4` thì `P=10/3`
