grade 11 applied math

Question

Build a quadratic function that points down and has roots 2 and -4.

Marks may be awarded as outlined below. If your teacher plans to use a different strategy to evaluate your work they will inform you before you start the assignment.
Unless you are instructed differently this assignment is worth 4 marks. Use the following information to guide your work:

1 mark for setting up the quadratic equation properly
1 mark for showing appropriate work to find the equation
1 mark for a quadratic function with roots 2 and -4
1 mark for a quadratic function that points down

Answer 1

y(x) = a(x - 2)(x +  4) = a(x^2  + 2x - 8) = a[(x^2 + 2x + 1) - 1] - 8a;  then:  y(x) = a(x + 1)^2  - 9a;  choose a = -1

 

then:  y(x) = -(x + 1)^2 + 9