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Maths- solve 4^x=9 giving your answer to 3dp

solve 4^x=9 giving your answer to 3dp (3 marks)
is this to do with logs? how do i do it

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Reply 1
Original post by dongonaeatu
solve 4^x=9 giving your answer to 3dp (3 marks)
is this to do with logs? how do i do it


log49 = ?

Just remember 23=8
and log28 = 3
Reply 2
It is indeed. Take logs of both sides

so xlog4=log9
Reply 3
Original post by dongonaeatu
solve 4^x=9 giving your answer to 3dp (3 marks)
is this to do with logs? how do i do it


Start with taking logs of both sides and then see if you can rearrange to get x=
Reply 4
yes it is

take logs of both sides

use the rule log(ab) = blog(a)
Reply 5
Original post by TenOfThem
yes it is

take logs of both sides

use the rule log(ab) = blog(a)


i get 1.584962501

to 3dp is it: 1.585
Reply 6
Original post by J10
It is indeed. Take logs of both sides

so xlog4=log9


1.585 is that the answer for x
Reply 7
Original post by dongonaeatu
1.585 is that the answer for x


Yep :smile:

Also without a calculator you know 4^1 = 4 and 4^2 = 16 so x is going to be between 1 and 2 so 1.585 sounds sensible. A useful check if you don't have a calculator :wink:
Original post by TenOfThem
yes it is

take logs of both sides

use the rule log(ab) = blog(a)

Superscripted :wink:
Reply 9
Original post by TheGrinningSkull
Superscripted :wink:


hey man is turning point the same as stationary point?
Original post by dongonaeatu
hey man is turning point the same as stationary point?


For the most part, yes
You should really pay more attention in class.
Original post by Lilium
You should really pay more attention in class.


LoL

I expect that to become your sig ... :biggrin:
Original post by dongonaeatu
hey man is turning point the same as stationary point?


Like TenOfThem said, for the most part yes, turning points are when you have minimums and maximums where the gradient changes at the stationary point, however this isn't always the case such as points of inflection.
Original post by nm786
log4x=log9[br]xlog4=log9[br]thereforelog9/log4=x[br]x=1.58log4^x=log9[br]xlog4=log9[br]therefore log9/log4=x[br]x=1.58


You're a bit late to the party. Also, 3dp.
Reply 15
Original post by Contrad!ction.
You're a bit late to the party. Also, 3dp.
yeah. :biggrin:
i thought it said 3sf :tongue:
Reply 16
Original post by nm786
yeah. :biggrin:
i thought it said 3sf :tongue:


even if it was 3 significant figures wouldn't it be 1.59 instead of 1.58
Original post by nm786
yeah. :biggrin:
i thought it said 3sf :tongue:


Haha sneaky edit. I'm a chronic misreader so I suppose I can't really talk :biggrin:

Like in C2 where I ended up losing out on full UMS because of it :ninja:
Reply 18
Original post by zed963
even if it was 3 significant figures wouldn't it be 1.59 instead of 1.58

no it would be 1.58 as there is a 4 after it and 4 is less than 5,
Original post by zed963
even if it was 3 significant figures wouldn't it be 1.59 instead of 1.58


Nope, it's 1.58496...... so 3sf = 1.58 and 3dp = 1.585.

When I saw that, I checked :tongue:

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