Answer
g(x) = (1/3 x)^2
Explanation
The original point was 1,1 in the f(x) function.
The transformed point is 3,1 in the g(x) function.
So the x value has been multiplied by 3.
This means g(x) = (1/3x)^2
It has to be in the brackets as it involves the stretch of the x value not the y value.
It’s also 1/3 because if it is in the inner brackets then it does the opposite to x so
x / 1/3 = 3x
<~>\_/<~> Ho_odini <~>\_/<~>