The domain is all possible values of 'x' that would make the function true. As you can see from the graph, this function goes out to infinity both ways, so all values of 'x' will satisfy the function, so your answer should be:
The error is in the first step. It should be (+8 plus or minus the square root of the quantity eight squared minus four times one times seven ). This is because "b" is -8 so -b is -(-8) = +8
While I do not know what the function is, if you want to translate the function down 5 units, you will take the equation of the function and subtract 5 at the end.
The answer is 44 if I’m not mistaken