Solve for x log3 (x-2) + log3 (x-4) = 7

[nae99]

 

[SammyS]

oh i see ok. so it should be;

x = -(-6) $\pm$ $\sqrt{}$ -6^2 - 4*1*-2179 $/$ 2*1

Use enough parentheses to make your expressions say what you mean.

If you mean, x = {-(-6) ± √[(-6)^2 - 4*1*(-2179) ] }/ (2*1),

then, yes, you are right.

 

[nae99]

and now it will be:
x = -(-6) $\pm$ $\sqrt{}$ -36 - 8716 $/$ 2

ok thanks very much

 

[SammyS]

No,

What is (-6)² ?

What is -4*(1)*(-2179) ?

How were you taking the square root of negative numbers?

 

[Ray Vickson]

i don't know how to plug it into the equation

If log[a](b) denotes the base-a logarithm of b, then x = log[a](b) solves the equation a^x = b = (exp(ln(a))^x = exp(x*ln(a)), so x*ln(a) = ln(b). So, if you can compute ln then x = log[a](b) = ln(b)/ln(a). If you prefer to use base-10 logs, you would have, instead, log[a](b) = log[10](b)/log[10](a).

RGV

 

[nae99]

(-6)^2 = -36

-4*(1)*(-2179) = 8716

so should it be √ -36 + 8716 / 2

 

[nae99]

no,

what is (-6)² ?

What is -4*(1)*(-2179) ?

How were you taking the square root of negative numbers?

(-6)^2 = 36

-4*(1)*(-2179) = 8716

 

[BloodyFrozen]

Or you can use change of base. It might be a little tedious though...

 

[SammyS]

Or you can use change of base. It might be a little tedious though...

Have you looked at the previous posts in this thread? Change of base would appear to be a huge stretch if we are having this trouble with plugging into the quadratic formula.

 

[nae99]

Have you looked at the previous posts in this thread? Change of base would appear to be a huge stretch if we are having this trouble with plugging into the quadratic formula.

i don't have any how to plug it into anything, so I am clueless of what you u are talking about

 

[BloodyFrozen]

Have you looked at the previous posts in this thread? Change of base would appear to be a huge stretch if we are having this trouble with plugging into the quadratic formula.

Yeah, true...

(-6)^2 = -36
-4*(1)*(-2179) = 8716

so should it be √ -36 + 8716 / 2

(-6)^2 = (-1)^2*(6)^2 = 36
-6^2 = -1*(6)^2 = -36

P.S. Nae99, may I ask what kind of Pre-calc class (college, high school) you are taking?

 

[nae99]

Yeah, true...



(-6)^2 = (-1)^2*(6)^2 = 36
-6^2 = -1*(6)^2 = -36

P.S. Nae99, may I ask what kind of Pre-calc class (college, high school) you are taking?

college