Step-by-step explanation:
with your square root symbol I never know what is inside the square root and what is possibly outside.
so, I can only guess and see what comes close.
f(x) = 2x² + x - 1
g(x) = sqrt(2x - 1) ??? is that so ?
h(x) = -2
2g(f(x)) + h(x)
g(f(x)) means that the whole f(x) expression is used as x in g(x).
the whole combined function is then
2×sqrt(2(2x² + x - 1) - 1) - 2
2×sqrt(4x² + 2x - 2 - 1) - 2
2×sqrt(4x² + 2x - 3) - 2
and if I am not mistaken, then this is the solution you mentioned at the beginning (if I try to read between the typos and missing info).
this is how people get to this.
do you understand it now ? or is there still something unclear ?

Here, “p” is a numerator and “q” is a denominator. The examples of rational numbers are 6/5, 10/7, and so on. The rational number is represented using the letter “Q”. Like real numbers, the arithmetic operations, such as addition, subtraction, multiplication, and division are applicable to the rational numbers.
I think the error is that you did not divide 6 by 2 first because you are supposed to so you would get 3, then you do 1 times 3 which is 3, then you have 3 plus 3 left which would be 6. i’m hoping this is right and that it helps you