cubic polynomial fcn w/ f(1)=0, f(2)=3, constant term -5,...

[towlie536]

A cubic polynomial function f has leading coefficient 2 and constant term
-5. If f(1)=0 and f(2)=3, what is f(-5)? Explain how you found your answer.

I dont get how to set this up or solve it. Can anyone help?

 

[Deleted member 4993]

Re: A cubic polynomial function.. Help!

A cubic polynomial function f has leading coefficient 2 and constant term
-5. If f(1)=0 and f(2)=3, what is f(-5)? Explain how you found your answer.

I dont get how to set this up or solve it. Can anyone help?

A general cubic polynomial will look like:

\(\displaystyle a\cdot x^3\, + \, b\cdot x^2\, + \, c\cdot x\, + \,d\)

where a, b, c & d are unknown constants - that you need to find.

Your problem tells you

a = 2 and

d = -5

Now you have to find two more constants (b & c).

For that you are given two conditions (f(1) = 0 and f(2) =3). These will give you two equations and you solve for two unknowns.

Please show us your work and exactly where you are stuck - so that we can help you better.