Question

Give the smallest value of x for which the derivative of 3 f (x) = x + 3x + 2 is 0.
a. -1
b. 1
c. -2
d. 2
e. 0
f. None of these.
Entire class is worried abt this one! Isn't the answer f?

Answer 1

is that 3*f(x)?

Answer 2

sorry!

Answer 3

3f(x)=4x+2?

Answer 4

f(x) = x^3 +3x +2

Answer 5

great catch!

Answer 6

ok
f'(x)=3x^2+3
3x^2+3=0
3(x^2+1)=0
x^2+1=0
x=-1 and x=1
smallest is x=-1

Answer 7

oh I see, what you did! brilliant! makes complete sense, thanks.

Answer 8

lol
they just want the smallest value satisfying f'(x)=0

Answer 9

thats; what I did initially. Butm the entire class posted going nuts that it was f blah blah blah.... :-)

Answer 10

well gj next time you tell them that there all wrong lol

Answer 11

@.@ x^2+1=0 =>x is +i,-i isn't it?

Answer 12

omg i suck x^2+1=0
x= + or - i

Answer 13

i need to go to the bed
gj kiwi

Answer 14

so the class is right it is f

Answer 15

lol

Answer 16

haha

Answer 17

don't tell them they are wrong

Answer 18

haha

Answer 19

I need a little review... what's the derivative of a constant? is it 0?

Answer 20

yes kiwi

Answer 21

derivative=slope
slope of a horizontal line (y=c , c is constant) is 0
so the derivative is 0

Answer 22

thanks