1. ## Functions

If f(x) =2x^3 + Ax^2 + 4x - 5 and f(2) = 5, what is the value of A?

I keep getting = -31\2 but the correct answer is -7/2
how do I get that? :| thank you

2. Originally Posted by cokeclassic
If f(x) =2x^3 + Ax^2 + 4x - 5 and f(2) = 5, what is the value of A?

I keep getting = -31\2 but the correct answer is -7/2
how do I get that? :| thank you
$f(2) = 5$ means

$2(2)^3 + A(2)^2 + 4(2) - 5 = 5$

$\Rightarrow 16 + 4A + 8 - 5 = 5$

from here, simple arithmetic will get you the right answer (-7/2). want to try?

3. Oh opps... I multiplied 2 x 2 first

Thank you