f(x) = x^2 + 3

g(x) = sqrtx

fog(x) = f(g(x)

= f(sqrtx)

= (sqrtx)^2 + 3

= x+ 3

**==> fog(x) = x+ 3**

gof(x) = g(f(x)

= g(x^2 + 3)

= sqrt(x^2 + 3)

**==> gof(x) = sqrt(x^2 + 3)**

f(x) = x^2 + 3

g(x) = sqrtx

fog(x) = f(g(x)

= f(sqrtx)

= (sqrtx)^2 + 3

= x+ 3

**==> fog(x) = x+ 3**

gof(x) = g(f(x)

= g(x^2 + 3)

= sqrt(x^2 + 3)

**==> gof(x) = sqrt(x^2 + 3)**