What is the inverse of
[tex]f(x) = \sqrt{x} + 6[/tex]
for
[tex]x \geqslant 0[/tex]
?

A:
[tex]f(x) = (x - 6) {}^{2} [/tex]
B:
[tex]f(x) = x {}^{2} - 6[/tex]
C:
[tex]f(x) = x {}^{2} + 6[/tex]
D:
[tex]f(x) = \sqrt{x + 6} [/tex]
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