did i get these right?

[murkr]

the stress i had a few days has went down so much since i became a member here, i actually feel prepared for my test coming up thanks to all of you. out of the 45 problems these are the last few im having serious problems with, i wish i understood these instead of bugging you guys haha


i already got the right answers to the others "i think"
#20 answer = C
#21 answer = B
#22 answer = B


i scanned the packet, here are the few problems im having trouble with.

http://img708.imageshack.us/img708/3449 ... k33333.jpg

are these problem right? did i get the correct answers to #20 21 and 22?

 

[murkr]

can somone please verify these? i will not bump this again i hope someone can help me with these, my test is in a few days

 

[arthur ohlsten]

20 is correct
log[3+x]-log[x-5]=log 5
log { [3+x]/[x-5]=log 5
[3+x]/[x-5]=5
3+x=5x-25
28=4x
x=7
answer C
===============================
21 is correct
1/3 log base2[x+6]= log base 8[3x]

log base 8 [3x] = y
raise to power of 8
3x= 8^y but 8=2^3
3x=[2^3]^y
3x=2^3y take log base 2
log base 2 [3x]=3y
y=1/3 log base 2 [3x]
log base 8 [3x]= 1/3 log base 2 [3x]

1/3 log base 2[x+6]= 1/3 log base 2 [3x]
x+6=3x
2x=6
x=3
answer B
============================================================
22 is correct
log[x+4]=1- log x
log[x(x+4)] =1 take inverse log base 21
x^2+4x=21
x^2+4x-21=0
[x+7][x-3]=0
x=-7 or x=3

x=-7 is extraneous answer I believe because the log of negative values is multivalued
x=3
answer B
==========================================================
23
I don't understand the notation
sorry
====================================================
24
10=1+1.5 ln[x+1]
9=1.5 ln [x+1]
divide both sides by 1.5
6=ln[x+1]
e^6= x+1
x=e^6-1
x=403.4-1
x=402.4
answer C

Arthur