May 2010, TZ1 HELP

[Yahooo!]

Okay, so on the May 2010 paper, TZ1 there is a question on mapping, it is towards the end.

The question gives the domain and range, and it asks to find 2 equations, relating to the domain and range.

Normally this would be done using the LinReg APP on the Texas calculator, but the question asks for it the quadratic form. Any one know how to do this?

[Rahul]

Use a quadratic regression on calculator! However, it's a paper 1.

So we're going to calculate this via regression for a polynomial of the form ax^2+bx

y=ax^2+bx

Plug the point (1,8) in:

8=a+b

Plug (2,20) in:

20=4a+2b

10=2a+b

Solve the system:

10=2a+b

8=a+b

2=a

6=b

Thus, the equation is f(x)=2*x^2+6x.

Then the vertex is simply -b/2a, or -6/4, thus -3/2 is the x-coordinate.