Techniques for Solving Logarithmic Equations

[AlRichards314]

An even number of negatives multiplies to give a positive. (-3)(-3)(-3)(-3) = + 81

[Sub4SubbingMe]

-3 to the power of 4 is a positive? Can someone explain?

[elcristube]

tnx,,,,i understND IT NOW.......

[FirstGradeCalculus]

What a great lesson! Nice graphics as well!

[Hitman2220]

this is all easy for me, its just when the base of log isnt 10 that confuses me.

[arimandler]

excellent video!

[addyd22]

Thank youu soo much!

I now finally get it!

Ps my semester exam is tomorrow!

[iluvmypitty]

thank you so much! that sure was a lot easier than many other videos made it out to be

[100592j]

i have some simple math for you all 10mins of youtube > a whole week in class

[YAKUBDZHANOVA21]

thank you so much, helped me a lot! My teacher does NOT explain like you do, he just expects us to know things, that i had never seen in my life before lol.. : )

[hannarimbi]

helppp! log a (3x+5)=2 find x.

[AlRichards314]

@hannarimbi To solve for x rewrite this in its equivalent exponential form. That would be 3x + 5 = a^2, so 3x = a^2 - 5 and x = (a^2 - 5)/3.

[headhunter0420]

this is a great video. thank you. my teacher is a fucking asshole and doesnt teach properly.

[vede1994]

thanks mate

[pyrodudewasa]

can someone help me how to get the components in order to graph:  f(x)=ln((x+2)/(9x-8)) ive been looking for a program to graph this but it does not recognize it... HELP PLEASE i need this for tomorow... atleast some link to a program or a similar tutorial vid of these types of logs

[AlRichards314]

@pyrodudewasa I graphed this function using my graphing calculator. It has a vertical asymptote at x = -2, and another at x = 8/9. The graph does not exist between the asymptotes since the (x+2)/(9x - 8) part is always negative there (you can't take the ln of a negative). There's also a horizontal asymptote at about x = -2.2. If you send me your email address I'll send you an image of the graph.

[TheLoveformankind]

U R BEST TEACHER EVER

[cooldude8081]

This video was awesome....helped me a lot :-)

[SimkeRULZ]

I'm not quite sure about America and EU, but in Serbia and Croatia we do this at the age of 15!

[737FSPilot]

you are a life saver!

[evangrooms1]

thank you this helped me alot

[evangrooms1]

thank you this helped me alot

[nickey9090]

I have a question about solving a logarithmic functions. Here what i am fighting with

f(x)=-(ln(x)+1/x+135). If you'll be able to solve this, please send the solution to nickdoban@yahoo.com I'll really appreciate your help. Thanks in advance

[BearOnBear]

All four types! THANK YOU!

[satfreegames]

bro you a boss man

thank you !

[zodiark111]

Oh my God dude, thanks my huge test is tommorow and you've finally explained to me what no one else has been able to.

[twowayradios45]

on example c, i did the full check and -2 ended up multiplying -5 to get 10....wouldn't that work if it was 10^=10?

[AlRichards314]

@twowayradios45 While the -4 root may satisfy the quadratic equation x^2 + x - 12 = 0, it cannot be a root of the logarithmic equation. The log(x + 2) and log(x - 1) expressions both become undefined when you replace x with -4 in them. log(-4 +2) = log(-2) and log(-4 - 1) = log(-5) which both are undefined. The reason they are undefined is that taking a log of a negative means you could evaluate a positive base to some exponent and get a negative, which is impossible.

[twowayradios45]

i realized my mistake nvm but thanks for the reply!

[flynig1]

You are very good at this. I understand it completely now thanks

[kmcnolo]

Thank you! very helpful!

[wakefan63]

Is there a way to know when to use the cancellation property?

[AlRichards314]

@wakefan63

If, by the cancellation property you mean when you drop the logs and equate what's left that's the main idea when solving log equations. It comes from the idea that if log A = log B, then A = B. You aren't really cancelling the logs, just equating the A and B since they must be equal. It is the same idea when solving exponential equations. If you have 3^2x = 3^8, then since the bases are the same then 2x = 8 and we can solve for x and get x = 4.

[luckyblondieo]

My test is tomorrow, and you just owned my teachers week of explanation in less than 10 mins..bravo! :)

[ashlylove26]

that was great thanks a lot! (:

[jesusclau1]

You'r absolutely amazing at how to explain Math problems in a very consice, clear way. I love your vids. Thank you so much!!!

[ChasingKomodo]

what do you do if the logs in the equations that you are adding or subtracting have different bases?

[AlRichards314]

These techniques only work if the bases are the same. If they are not the same there is a change of base formula, but that can get messy.

[cooldude8081]

@AlRichards314, is this Algebra 1 or 2?

[AlRichards314]

@cooldude8081 This video was created for a math course in the province of Ontario, Canada. Sorry, I'm not familiar with the curriculum of Algebra 1 or 2.

[barbaloom]

Thank you!