Answer:
You are correct, except that 12.72 should be positive, not negative.
max = (140/11, 49/11)
Step-by-step explanation:
We got the same answer, but I used a different method.
The max point of a parabola is found when its derivative is equal to 0 because the slope at the max point is neither increasing or decreasing.
I just solved for when the derivative is 0 and got
max = (140/11, 49/11)
or (12.727272, 4.45)
I highly recommend you always leave your answers as a fraction unless they specify you to give a decimal answer. Rounding is never good in math or physic because it could lead to errors in bigger problems.