<span>Using
the points (2, 45) (4, 143) and (10, 869), we can plug them into the
following system of 3 equations using the y = ax^2 + bx + c format:
45 = a(2)^2 + b(2) + c
143 = a(4)^2 + b(4) + c
869 = a(10)^2 + b(10) + c
which simplifies to:
45 = 4a + 2b + c
143 = 16a + 4b + c
869 = 100a + 10b + c
Solving the system, we get a = 9, b = -5, and c = 19. Thus the equation is:
c(x) = 9x^2 - 5x + 19
If you have a TI graphing calculator, you can also enter the points by
pressing Stat -> Edit and enter (2, 45) (4, 143) and (10, 869) into
it. Go back and calculate the QuadReg of the points from the Calc tab
and it will give you the same answer.
Now that we know the function that will produce the price of production
for any number of calculators, plug in x = 7 and it will give you the
price to produce 7 calculators.
