Question

I want to know if i am rite
4. The total consumption of fossil fuels in the United States per year can be represented by the function C(x) = 0.0439x3 – 1.4911x2 + 14.224x + 41.76, where x is the number of years after 1970, and C(x) represents the amount of energy consumed in quadrillions of BTUs (or “quads”). In 1979, the U.S. consumed 81 quads of energy.

Subtract C(x) – 81 and write down the resulting function. Since you know that 9 is a root of this function, find the other two roots. In what year after 1979 did the U.S. consumption of energy also reach 81 quads?

Answer 1

looks good to me. want the computation?

Answer 2

can you work this problem out?

Answer 3

well except it is not what i get

Answer 4

bare with me, i going write i have so far

Answer 5

let me try again and make sure i have it correct

Answer 6

C(x) = 0.0439x3 – 1.4911x2 + 14.224x + 41.76

Answer 7

so what you do is, substract 81 from 41.79

Answer 8

\[C(x)=.0439x^3-1.4991x^2+14.224x+41.76\] is that right?

Answer 9

i mean before you subtract is that correct?

Answer 10

you going have c(c) 0.0439x^3-1.4911x^2+14.224-39.28
now you use syntethic divicion,
we know 9 is a root of this function

Answer 11

yes that would be correct. if C(9) = 81

Answer 12

9] 0.0439 -1.4911 +14.224 -39.28

Answer 13

but it doesn't seem to be according to my calculation let me check again

Answer 14

no the first question

Answer 15

when you do syntethic division, you get 0

Answer 16

then you are correct!

Answer 17

and teh giving you an extreme equation, and know you can find both root,


0.0439^2-1.096x+8.36

Answer 18

you did the syntethinc division, and you got 0, correct?

Answer 19

you did the syntethinc division, and you got 0, correct?

Answer 20

you did the syntethinc division, and you got 0, correct?

Answer 21

must be typing something in wrong because i do not get zero

Answer 22

ok , type what you doing

Answer 23

close, but i get C(9)=-.04 but that is probably close enough.
you get 0 exactly?

Answer 24

so you get 0?

Answer 25

close to 0 , is not enough..

Answer 26

ooho i see

Answer 27

41.76-81=-39.24 not -39.28

Answer 28

le't try it again, 9] 0.0439 -1.4911 +14.224 +39.28

Answer 29

last number should be 39.24

Answer 30

use your calculator, i dont knohere mine is

Answer 31

then it will work

Answer 32

i did and it works

Answer 33

oh good, oh graph, yeah is -39.24, i thought it was an 8

Answer 34

whew. then you get 0 i checked already

Answer 35

get \[0.04390*x^2-1.096x+4.36\]

Answer 36

yeah, now what, guadratic formula?

Answer 37

yes what a pain. hold on and i will cheat if you like

Answer 38

lol

Answer 39

ikr, better then factoring at least...

Answer 40

looks like x=20 or x = 4.966 rounded

Answer 41

a miracle. 20 is exact!

Answer 42

so going back to the problem, those are the root, you did quadratic formula?lol

Answer 43

we must bei n the right tract

Answer 44

so it must factor as \[(x-20)(.0439x-.218)\]

Answer 45

no i didn't use the quadratic formula because i would have no patience for that

Answer 46

i used maple

Answer 47

lol, so wee know both root that were missing, the is really the aswner?

Answer 48

yup that is it

Answer 49

just changing them to word, and the will do it, thx man.

Answer 50

must be. you can check easily (more or less) that 20 is a zero of
\[.0439x^2-1.096x+4.36\] so as you know it must factor as \[(x-20)(something)\] and you have no choice for the something

Answer 51

good luck

Answer 52

oh crap, we are not,done, remember it ask you in qhat yesterday,

Answer 53

oh crap, we are not,done, remember it ask you in qhat yesterday,

Answer 54

oh crap, we are not,done, remember it ask you in qhat yesterday,

Answer 55

oh crap, we are not,done, remember it ask you in qhat yesterday,

Answer 56

oh crap, we are not,done, remember it ask you in qhat yesterday,

Answer 57

lol, lagg, year*

Answer 58

lol, lagg, year*

Answer 59

you still here?