It can be any number from 450000 to 549999. This is due to the fact that
when figures like this are reported they are either rounded up or down.
Answer: y=0,5x²-x-1,5.
Step-by-step explanation:

We summarize (1) and (3):

Substitute b=-1 into (2):

From (5) subtract (4):

Substitute a=0,5 into (4):

Hense:
y=0,5x²-x-1,5.
It's just asking for the gradient basically
150/3 = 50
Or technically -50 because it's decreasing