Question 685987
f(x)={{{sqrt(3x)}}} ; g(x)={{{sqrt(12x)}}}
solve:
(f+g)(x)={{{sqrt(3x)+sqrt(12x)}}}
(f+g)(x)={{{sqrt(3x)+sqrt(4*3x)}}}
(f+g)(x)={{{sqrt(3x)+2sqrt(3x)}}}
(f+g)(x)={{{highlight(3sqrt(3x))}}}
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Explanation....first you simplify the radicals.  You can only add and subtract like terms.  Radicals are only like terms when the indexes and roots are exactly the same.
Happy Calculating!