`a)`
`x^2- 22`
` = x^2 - (\sqrt{22})^2`
` = (x-\sqrt{22}) . (x + \sqrt{22})`
`b)`
`x^2 - 2 \sqrt{23} x + 23`
` = x^2 - 2 . x . \sqrt{23} + (\sqrt{23})^2`
` = (x -23)^2`
`c)`
`x^2 - 9 \sqrt{x} + 14`
` = x^2 - 2 \sqrt{x} - 7 \sqrt{x} + 14`
` = \sqrt{x} . (\sqrt{x} -2) - 7 . (\sqrt{x} -2)`
` = (\sqrt{x} - 7) . (\sqrt{x} -2)`