Question

Use the following equation:
log2x + log2(x – 7) = 3

The answer to the function would be:
Select one:
a. 8
b. –1
c. 8 or –1
d. –8 or 1

Answer 1

You can use here:

\[\log(a) + \log(b) = \log(a \times b)\]

Answer 2

well here is a tip... you can't find the log of a negative number....

so that should help identify the answer

Answer 3

is 2 in base @chantz417

Answer 4

Yes sorry just got back

Answer 5

where 2 is in base of logarithm

Answer 6

u there @chantz417

Answer 7

lol... how can you substitute x = -1

what is the value of

\[\log_{2}(-1) =..?\]

Answer 8

wow... understand some basics of logarithms

Answer 9

you can after u make it log(x(x-7)) after that u get x(x-7) > 0 implying x can be either greater then 7 or less than -1 read logarithms and functions carefully @campbell_st

Answer 10

u can just put x=-1 in logx that's wrong but you can after u make x(x-7) as it will come out positive @campbell_st

Answer 11

can't* not can typed wrongly

Answer 12

have a look at the original equation

you get

\[\log_{2}( -1) + \log(-1 - 7) = 3\]

tell me how that works...

Answer 13

the only solution is 8....

Answer 14

seperately it doesn't but if u make it something like this log(-1)(-1-7)

Answer 15

so i missed u clicked u are right we must see it other perspective as well @campbell_st
gud luck !!!

Answer 16

just test the solution in the original equation... the only solution that works is x = 8

Answer 17

ans 8 only

Answer 18

you are provided with the answer choices.... the easy solution with out calculation or algebraic manipulation is substitution...

so substitute the choices and see what you get

Answer 19

not every one is that intelligent @campbell_st you need to xplain others

Answer 20

u and i can do that but not every one

Answer 21

well I'm in high school... and have been taught to always check the solutions make sense.

Answer 22

it's ohk but doesn't always work that way @campbell_st still u have a long way to go

Answer 23

u will get options sometimes u can't just check them out

Answer 24

lol... why make things hard.... use the obvious... another good problem solving skill.

Answer 25

u'll learn why to solve ... later it might look that easy today .... @campbell_st