Question

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

The third step would be to:


Select one:


a. Graph the function.

b. Take the log of each side.

c. Square the expression.

d. Factor the resulting quadratic equation.

Answer 1

log_a (b) + log_a (c) = log_a (b times c)

Answer 2

so the answer B would be the first step right

Answer 3

Nope

Answer 4

\(\normalsize\color{blue}{ \log_2x + \log_2(x – 7) = 3\LARGE\color{white}{ \rm │ }}\)

Step 1. \(\normalsize\color{blue}{ \log_2~x(x – 7) = 3\LARGE\color{white}{ \rm │ }}\)

Step 2. \(\normalsize\color{blue}{ \log_2~x^2-7x = 3\LARGE\color{white}{ \rm │ }}\)

Step 3. \(\normalsize\color{blue}{ 2^3=x^2-7x\LARGE\color{white}{ \rm │ }}\)

Step 4. \(\normalsize\color{blue}{ 9=x^2-7x\LARGE\color{white}{ \rm │ }}\)

Step 5. \(\normalsize\color{blue}{ 0=x^2-7x-9\LARGE\color{white}{ \rm │ }}\)

Answer 5

This is what I would do to solve it.

Answer 6

So step 2 is Square the expression correct

Answer 7

it's now square, It's property of log

Answer 8

No, I am multiplying inside the log.

Answer 9

but then, I am using a "log-relation" (or whatever it is actually called)

Answer 10

So the answer is?

Answer 11

So b is the answer then @SolomonZelman

Answer 12

You aren't taking the log of each side, are you ?

Answer 13

or if you do, you get "log of log" on the left.

Answer 14

So what would it be @SolomonZelman

Answer 15

It is hardly any of the choices.
Not A, because there is no need graphing to find the solution.
Not B, because you aren't logging both sides.
C -- don't get it.
D, is it.

2^3 = 8 (not 9, sorry)

Answer 16

So you would get

x^2-7x-8=0
(x-8)(x+1)=0
x=8,-1

Answer 17

Sorry one more time... makes sense now ?