The answer to that one is C
At the equilibrium price p, we can solve for the quantity of goods x :
demand = supply
5200 - 0.0005x = 2800 + 0.0003x
2400 = 0.0008x
x = 3,000,000
With this quantity of goods, the equilibrium price is
p = 5200 - 0.0005 (3,000,000)
p = 5200 - 1500
p = 3700
The standard form of a parabola is y=ax²+bx+c
use the three given points to find the three unknown constants a, b, and c:
-2=a+b+c............1
-2=4a+2b+c......... 2
-4=9a+3b+c...........3
equation 2 minus equation 1: 3a+b=0..........4
equation 3 minus equation 2: 5a+b=-2.........5
equation 5 minus equation 4: 2a=-2, so a=-1
plug a=-1 in equation 4: -3+b=0, so b=3
Plug a=-1, b=3 in equation 1: -2=-1+3+c, so c=-4
the parabola is y=-x²+3x-4
double check: when x=1, y=-1+3-4=-2
when x=2, y=-4+6-4=-2
when x=3, y=-9+9-4=-4
Yes.
