How do I use log here?
75000 * .96^x = 50000 * 1.07^x
x = ?

Question

How do I use log here?
75000 * .96^x = 50000 * 1.07^x
x = ?

saifoo.khan · Answer

$$0.96^x = \frac{50000}{75000} * 1.07^x$$
$$0.96^x = \frac23 * 1.07^x$$

saifoo.khan · Answer

Radar will continue from here.

radar · Answer

Hey I was in the learning mode, keep on please.

saifoo.khan · Answer

Lol, i forgot how to solve these. Hold a sec. let me get back my memory.

radar · Answer

I don't think I ever knew lol

saifoo.khan · Answer

we have to "suppose a particular value for this)
Let me get my register real fast.

saifoo.khan · Answer

Called 911 for help.

bahrom7893 · Answer

take ln on both sides

saifoo.khan · Answer

Still stuck..

bahrom7893 · Answer

75000 * .96^x = 50000 * 1.07^x
ln(75000 * .96^x) = ln(50000 * 1.07^x)

bahrom7893 · Answer

Saifoo please let me finish

bahrom7893 · Answer

ln75000+ln0.96^x = ln50000+ln1.07^x

bahrom7893 · Answer

xln0.96 - xln1.07 =ln50000-ln75000

bahrom7893 · Answer

x(ln0.96-ln1.07) = ln50000-ln75000

bahrom7893 · Answer

x = (ln50000-ln75000)/(ln0.96-ln1.07)
finish the algebra

anonymous · Answer

why the natural log, could you use regular log?

bahrom7893 · Answer

lol u can i guess, it's just that im so used to natural logs.

bahrom7893 · Answer

In calc u barely use any other logs. I'm really used to natural logs, lol it feels natural.

anonymous · Answer

so if I substituted log in for each ln it would give me the same answer?

bahrom7893 · Answer

it should

anonymous · Answer

ahah that's really punny stuff

radar · Answer

I will attempt and then saifoo.khan can correct me.
Continuing with the last equation.  Dividing both sides by 0.96^x getting
1=2/3 * 1.07^x/.96^x   multiplying both sides by 3/2, we can now write it as
3/2=(1.07/.96)^x simplfying
1.5=1.1146^x
log 1.5= x log 1.1146
.1761 = x *.04712
x=3.7

anonymous · Answer

what if the question had said 10000 + .96^x = 1.07^x

bahrom7893 · Answer

hmm then throw 0.96^x to the right and take log on both sides.

bahrom7893 · Answer

wait a second..

radar · Answer

It is probably closer  to 4 as I rounded off the log values.

radar · Answer

Wolfram shows 4.

bahrom7893 · Answer

btw idk what happens if it's pluses, logs wont work, ull need a calculator.

anonymous · Answer

oh I see what i did wrong, thanks for showing me how guys

bahrom7893 · Answer

http://www.polyvore.com/cgi/img-thing?.out=jpg&size=l&tid=31489685 lol sorry, but ur last post asked for this hahahaaha

anonymous · Answer

rofl