Mathematics: Post your doubts here!

[john10]

how to do???

 

[leadingguy]

how to do???
View attachment 13919

what is the ans ?? post ans as well.

 

[leadingguy]

how to do???
View attachment 13919

5^(2x-1) =2(3)^x

(2x-1)lg5 = 2(3^x)

2xlg5 - lg5 = lg2 +xlg3

xlg5^2 -xlg3 = lg2 + lg5

xlg(25/3) = lg(2*5)

xlg(8.33) = lg10

xlg(8.33) = 1

x(0.921) = 1

x = 1/(0.921)
x = 1.09 Ans

 

[leadingguy]

parthrocks

16/[(2+x)^2]



16*[ (2+x)^ -2]

16*[2^ -2 (1+1/2x)^-2]

4*[(1+1/2x)^-2]

now abbpy binomial theoram on the curly brackets

4*[1 +nx + n(n-1)x^2/2!.............]

4*[1 + (-2)(1/2x) + {(-2)(-2-1)(1/2x)^2}/2!].


4*[1 - x + 3/4 x^2]


4 - 4x + 3x^2 Ans



hope it is clear???

 

[leadingguy]

parthrocks

m/j 2011 qstn 2

lg2(x+5) = 5 - lg2(x)

lg2(x+5) + lg2(x) = 5

taking lg2 as comman.

lg2{(x+5)*x} = 5

now as L.H.S is with lg base 2 so we have to convert the other side with base 2 as well.

look here....... lg22^5 = 5*lg22 = 5 (as lg22 is always 1 )

means lg22^5 = 5*lg22 = 5 = lg232

put this in the eq.



lg2{(x+5)*x} = lg232

now remove logarithim from both sides u will get
x^2 + 5x = 32 shown Ans

 

[john10]

5^(2x-1) =2(3)^x

thank u friend. it really helped. ya from now onwards, will post answers as well.

 

[parthrocks]

can anyone help me with some logarithmssssssssssss

and also chapter 4 in p2 and p3

 

[smzimran]

Stop spamming the thread!
Moderators take note plz, Nibz SalmanPakRocks CaptainDanger

 

[CaptainDanger]

parthrocks : Don't do that again! I merged your posts.

 

[parthrocks]

parthrocks : Don't do that again! I merged your posts.

sorry i was a bit hyper at that time.....

 

[shanky631]

5^(2x-1) =2(3)^x

if we use LN, is it the same???

 

[anishh]

yes bro it would be the same

 

[shanky631]

The correct ans is 0.313 but i don't get it. plz solve someone. Thnx in advance

 

[shanky631]

yes bro it would be the same

ya actually. thank u for clarifying my doubt.

 

[smzimran]

View attachment 13935

The correct ans is 0.313 but i don't get it. plz solve someone. Thnx in advance

ln (x+2) - ln x = 2
ln ((x + 2) / 2) = 2
(x + 2) / 2 = e^2


x + 2 = 2 e^2
x = 2 (e^2 - 1)

 

[shanky631]

ln (x+2) - ln x = 2
ln ((x + 2) / 2) = 2
(x + 2) / 2 = e^2


x + 2 = 2 e^2
x = 2 (e^2 - 1)

but u not getting the right answer. and shouldn't it be ln((x+2)/x)=2

 

[shanky631]

i think that is the only mistake. Rest is right. Thank u smzimran.

 

[Minato112]

ln (x+2) - ln x = 2
ln ((x + 2) / 2) = 2
(x + 2) / 2 = e^2


x + 2 = 2 e^2
x = 2 (e^2 - 1)

but u not getting the right answer. and shouldn't it be ln((x+2)/x)=2

ln ((x + 2) / x) = 2
(x + 2) / x = e^2
x+2= (e^2)*x
((e^2)*x)-x=2
x((e^2)-1) = 2
x = 2/ ((e^2)-1)
= 0.313

 

[smzimran]

ln ((x + 2) / x) = 2
(x + 2) / x = e^2
x+2= (e^2)*x
((e^2)*x)-x=2
x((e^2)-1) = 2
x = 2/ ((e^2)-1)
= 0.313

i think that is the only mistake. Rest is right. Thank u smzimran.

Yes, i did a little mistake, copied 2 in the denominator instead of x, rest is right!
minato112 has done the correct method, check it out!

 

[shanky631]

statistics Chapter 2 doubt. How to solve Q1???