# function of x

• Jan 8th 2009, 09:17 AM
RubbishAtMaths
function of x
you are given that $f(x)=x^3+kx+c$ the value of f(0) is 6, and $x - 2$ is a factor of f(x)

Find the values of k and c

ok i dont understand these at all, probably the last thing i have to revise and its my worst enemy. can someone explain??? thank yoouu (Wink)
• Jan 8th 2009, 09:32 AM
masters
Quote:

Originally Posted by RubbishAtMaths
you are given that $f(x)=x^3+kx+c$ the value of f(0) is 6, and $x - 2$ is a factor of f(x)

Find the values of k and c

ok i dont understand these at all, probably the last thing i have to revise and its my worst enemy. can someone explain??? thank yoouu (Wink)

Hello Rubbish,

$f(x)=x^3+kx+c$

$f(0)=6 \Longrightarrow 0^3+k(0)+c=6 \Longrightarrow \boxed{c=6}$

If $x-2$ is a factor of $f(x)=x^3+kx+c$, then $f(2)=0$

$f(2)=0 \Longrightarrow 2^3+2k+6=0 \Longrightarrow \boxed{k=-7}$
• Jan 8th 2009, 09:36 AM
RubbishAtMaths
muchly obliged govener, think i get em now (Happy)