precalc help(double check plz)

[nfow]

I need some help. I am taking precalc over the summer and it's moving so fast. Our midterm exam is next week and my teacher gave us this practice test to take home. It would be really helpful if you guys can do some of the problem and show all the steps. If i can see all the steps I can study off this practice test. Thank.

here is the practice test.

http://nfow00.homestead.com/files/math.rar

[Huyenthoai99]

what do I open it with??? I don't have that soft to open the RaR hihihihihi
....

It's much better to post them here NFlow!!!

[The Rock]

I've got to say that having people work out everything only helps you a bit in the situation that you are absolutely clueless on what to do. The only good way to learn and do well on the exam is by understanding the concepts and knowing what to do to solve the problems. Having said that, I'm only going to tell you how to solve some problems, especially those that don't require me to literally work them out. The answer isn't very important, but it is very important that you know how to solve a problem. You should do the tedious work to get to the answer because that's your job and you might understand and learn more by doing it.

Some words of advice, type up the questions IN PLAIN TEXT and post them here. People would help you if they see them easily. Only scan the ones with graphs and stuff because downloading data files takes time. Think about it, most people wouldn't put the effort to first download and then take a look at them like I did. People could read you as insincere because you scanned everything.

#1) f o f (x)?? Is there a typo somewhere 'cuz why is g(x) given but not mentioned? Substituting f for f results in INFINITE substitutions, so pick your best answer accordingly

#2) The percentages are just numbers (75% = 75, 25% = .25, etc...). Graph the given function by calculator, set the window as told and look at the far right. Notice what the range (the y's) converges to and that's your answer.

#4) To do f inverse, replace y by x and x by y, then solve for y and graph it. f inverse becomes this y = x - 1. By inspection it should be the graph labeled III

#5) the "behavior" is determined by the term with the highest degree, which is - 1/2 x^3 in this case. If you don't already have a mental picture of how x^3 graph it and see. The - flips the graph over the y axis. So the left end behavior is left and up; the right end behavior is right and down

#9) Notice -2 slope and y-intercept of 4 and sketch it

#13) g(x) = - (x - 2) ^ 2. Form a mental picture of f(x) = x^2 (if don't already know, cheat by graphing it) The negative slope flips the parabola down, and the (x - 2) shifts f(x) 2 units to the right.

#15) slope-intercept form is this form: y= mx + b. Translate the given eq. into that form.

Anyway, try the rest and ask about the ones that you're stuck on

[minibini]

#1) f o f (x)?? Is there a typo somewhere 'cuz why is g(x) given but not mentioned? Substituting f for f results in INFINITE substitutions, so pick your best answer accordingly

I don't think it is a typo.
f o f (x)... f(x) = sqr(x) + 5, f o f (x) is the same thing as f(f(x))... f(f(x)) = sqr(sqr(x) + 5) + 5 <=== this corresponds to D


#6) just graph the equation and trace the graph for x when y = 0, you'll get .62 and 1.38.


#7) same process as # 4 , to graph it.... juts plug in some easy #s.. like when x is 1... y is .25 or 1/4... when x is .5 .. y = 1/(4*.5) = 1/2 .. which is .5... .5 is bigger than .25... so as x gets closer to 0... it gets bigger... oh yeah x can't be 0.. since it will make hte problem undefined.... easier to identify this.. use graphing cal. or get familiar with the 1/x graph. :)

#8) graph 2 graphs.. 1 is the (x+7)/3x-1 = F(X) and the other is just 1... and trace the points where it hits 1.. and think logically.. hihi.. anything on the graph is above one.. meaning
F(X) > 1... else F(X)< 1..... The answer is D... open interval, I might be wrong too, since I was never good @ open and closed interval.

#9) answer is I, y = -2x + 4..... on all the graphs only I has y-intercept @ +4 ... and its slope is -2... which is to the right one, down 2.. or to the left one, up 2 units.'

#10) take 29 divided it by 37.. and times 100... that will give u the percent. anwer is B

#11) graph it...you will see that it makes an upside down U shape.. x-intercepts is @ x = -3 and +3... f(x) >= 0.. therefore it must be a closed interval (includes the end points)... answer E

#12) solve for Y...
x^2 + 7*y^2 = 49
7*y^2 = 49 - x^2
y^2 = (49 - x^2)/7
y = +- squareroot((49-x^2)/7) or 49/7 - x^2/7
y = + - squareroot(7 - x^2/7)
Answer B


#13) answer III correspond to therock response

#14) (12/x) - 3 = (18/x) - 4
(12/x) - 3 + 4 = (18/x) -4 + 4
(12/x) + 1 = (18/x)
-12/x + 12/x + 1 = (18/x) - 12/x
1 = 6/x
1*x = (6/x) * x
x = 6

hi`hi`.. this is a little bitty too much.. :) which problems don't you get?

[nfow]

Thank, this is really helping me a lot.

Huyenthoai99, you can dl winrar here http://www.rarlab.com/

[sky]

wow, this is too much !! why don't you do everything and post your answer here. we'll try to look at it, and tell you whether it's wrong or right.
i asolutely agree with "the rock", if you want to pass the exam you should do all of these problems by yourself. if you get a wrong answer, just spend more time on it and asking yourself "why did you do wrong?"

[nfow]

Could you guys please double check on my work. Just a suggestion. If you planning to double check plz post what problem you goin to do so it dosn't have to be done by 2 ppl. Thank.




16)
(x + 4) (x+5) (-3)
(x ^2 + 9x + 20) (-3)
Not sure if I would x it by -3???

17)
4/x + 1 (<-) 3/x+2
LCD (x + 1) (x + 2)
4x + 8 (<-) 3x + 1
x (<-) -7

18)
discriminant = sqrt(b^2 - 4ac)
sqrt((-2)^2 -4(1/3)(3))
4 - 4(1/3) (3)=0
(C)

19)???

20) (B)

21)
(x - 2) (x + 1) = (x - 3)^2
x^2 - x - 2 = (x - 3) (x-3)
x^2 - x - 2 = x^2 - 6x + 9
5x = 11
x =11/5
(B)

22) B

23)D

24)????

25)
5x^2 - 2 = 3x
5x^2 - 3x - 2
(5x + 2) (x - 1)

5x + 2 =0
x = -2/5

x-1=0
x = 1

26) using synthetic division
-2 | 1 -6 -3 1
| -2 16 -26
-----------------------
1 -8 +13 -25
x^2 - 8 +13 - 25/x+2
(A)

27)D

28)How would i approach this?

29)????

30)e

31)???

32)
-3< 5- x / 2 (<-) 7

-6 < 5- x (<-) 14

-11 < -x (<-) -9
11 > x (>-) -9
-9 (<-) x < 11
(B)

33)(d)

34) -2 | 1 0 0 8
| -2 4 -8
------------------
1 -2 4 0

x^2 - 2x + 4
(E)

35)???

36)(b)

[sky]

hom nay nhieu day thoi, luc khac lam tiep

16)
(x + 4) (x+5) (-3)
(x ^2 + 9x + 20) (-3)
Not sure if I would x it by -3???

>>I think it looks like this f^-1([g^(-1){-3}], solve for it

17)
4/x + 1 (<-) 3/x+2
LCD (x + 1) (x + 2)
4x + 8 (<-) 3x + 1
x (<-) -7
should be 3x+3 <or= 4x+8 then solve for x
18)
discriminant = sqrt(b^2 - 4ac)
sqrt((-2)^2 -4(1/3)(3))
4 - 4(1/3) (3)=0
(C)
ok
19)replace the value of x for -1
f(-1) = 2/(-1+3)= you can solve this

20) (B) ok

21)
(x - 2) (x + 1) = (x - 3)^2
x^2 - x - 2 = (x - 3) (x-3)
x^2 - x - 2 = x^2 - 6x + 9
5x = 11
x =11/5
(B)
ok

22) B ok

23)D. I don’t know, use a calculator to find it

24)????
Factor it
x^4+25x^2+144
let x^2 = y
therefore: y^2 + 25y + 144 (quadratic form)
(y+9)(y+16)
substitute x^2 for y
answer: (x^2+9)(x^2+16)


25)
5x^2 - 2 = 3x
5x^2 - 3x - 2
(5x + 2) (x - 1)

5x + 2 =0
x = -2/5

x-1=0
x = 1
OK
26) using synthetic division
-2 | 1 -6 -3 1
| -2 16 -26
-----------------------
1 -8 +13 -25
x^2 - 8 +13 - 25/x+2
(A)
I don’t remember this
27)D
calculator
28)How would i approach this?

(2-5x)^(1/2)=5x
square both side
2 – 5x = 25x^2
( quadratic form) you can solve this
29)????


30)e

[yeudoi]

16)
-----
Not sure if I would x it by -3???
----

Put x = -3 and evaluate after you found the inverse function.

yeudoi ba^.n wa' can't help.

[nfow]

Can some1 work out problem 28 and 29. thank

[sky]

i have a final test next week. i will try to solve all of these by next friday, if you want to wait. otherwise........ i don't know

[Chris-T]

Originally posted by nfow
Can some1 work out problem 28 and 29. thank

sq_root (2-5x) = 5x <------ square both sides

2 - 5x = (5x)^2
2 - 5x = 25x^2 <----- bring all to 1 side to make quadratic eq.

25x^2 + 5x -2 = 0 <--- quad-eq w/ a=25, b=5, c=-2.

Roots are (-b +/-#)/ 2a, where
#= sq_root (b^2 - 4ac)
#= sq_root (5^2 - 4*25*2) = sq_root ( 25 +200) = 15
Then
Root1 = (-5 + 15) / 50 = 10/50 = 1/5, and second root
Root2 = (-5 - 15) / 50 = -20/50 = -2/5

Answer is "B"

[Chris-T]

#29

3x - 2*sqrt(x) - 5 = 0
Look like quad eq but with the sq_root make us a little scary.
Anyway ==> let's call z = sqrt(x) as new variable then you'll have

3z^2 - 2z - 5 = 0 <---- this is quad eq.
(3z - 5)(z + 1) = <---- after factoring ==> 2 roots for "z"
z = 5/3, -1

Now solve for x with z = sqrt(x)
sqrt(x) = 5/3 ==> x = (5/3)^2 = 25/3 <----- First real root
sqrt(x) = -1 ==> Not Real (sqrt of something must be >=0)

Seem like "E" is your answer for this problem#29.

Double-check my work for any possible errors.

Good Lucks :flower: :flower: :flower:

[nfow]

Thank Chris-T. Nah that be alrite sky. Thank again to whoever help me out.