IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: immortal on April 20, 2010, 02:40:12 pm

Title: can any1 solve this maths question.
Post by: immortal on April 20, 2010, 02:40:12 pm: 3^(x+2)=3^x+3^2
Title: Re: can any1 solve this maths question.
Post by: Saladin on April 20, 2010, 02:49:15 pm: Working on it.
Title: Re: can any1 solve this maths question.
Post by: nid404 on April 20, 2010, 02:55:45 pm: base is the same

so x+2= (x+3)²
x+2 = x²+6x+9
x²+5x+7=0

solve the quadratic equation
u get x= -2.5
Title: Re: can any1 solve this maths question.
Post by: immortal on April 20, 2010, 04:22:15 pm: 3^x+2=3^x+3²

as per calculator, i get ans as 0.1072 (4s.f)
i wanna 2 kno how 2 derive at this ans.
Title: Re: can any1 solve this maths question.
Post by: nid404 on April 20, 2010, 04:29:41 pm: Quote from: immortal on April 20, 2010, 04:22:15 pm
3^x+2=3^x+3²

as per calculator, i get ans as 0.1072 (4s.f)
i wanna 2 kno how 2 derive at this ans.

I guess I haven't gotten ur question right then :-\

Is it
3^x+2=3^x+3²
or is it
3^x+2=3^(x+3)²
Title: Re: can any1 solve this maths question.
Post by: immortal on April 20, 2010, 04:34:16 pm: It's da 1st one 3^x+3=3^x+3²
tnk nid 4 ur help.
Title: Re: can any1 solve this maths question.
Post by: Saladin on April 20, 2010, 04:34:40 pm: Quote from: nid404 on April 20, 2010, 04:29:41 pm
I guess I haven't gotten ur question right then :-\

Is it
3^x+2=3^x+3²
or is it
3^x+2=3^(x+3)²

Thats is my question as well.
Title: Re: can any1 solve this maths question.
Post by: nid404 on April 20, 2010, 05:48:55 pm: not possible i think :-\
Title: Re: can any1 solve this maths question.
Post by: immortal on April 20, 2010, 07:34:07 pm: Cn any Ans this question,,PLZ :)
Title: Re: can any1 solve this maths question.
Post by: Saladin on April 20, 2010, 07:42:50 pm: The answer should be $x=-0.965$
Title: Re: can any1 solve this maths question.
Post by: nid404 on April 20, 2010, 07:43:52 pm: Quote from: Mister Mysterous on April 20, 2010, 07:42:50 pm
The answer should be $x=-0.965$

how would you derive that??
Title: Re: can any1 solve this maths question.
Post by: immortal on April 21, 2010, 03:45:54 pm: the ans is 0.1072 (4s.f) i think,cn any1 show da steps 2 derive at this :(
Title: Re: can any1 solve this maths question.
Post by: nid404 on April 21, 2010, 04:49:44 pm: Quote from: immortal on April 21, 2010, 03:45:54 pm
the ans is 0.1072 (4s.f) i think,cn any1 show da steps 2 derive at this :(

nope that can't be...i crosschecked
Title: Re: can any1 solve this maths question.
Post by: immortal on May 04, 2010, 12:56:50 pm: I got da ans.
3^x+2=3^x+3²
3^x*3²=3^x+3²
9*3^x=3^x+9
9*3^x-3^x=9
3^x(9-1)=9
3^x*8=9
3^x=9/8
x=ln(9/8)/ln3
x=0.107(3 s.f)

It cud also b done using iteration.
Title: Re: can any1 solve this maths question.
Post by: Ghost Of Highbury on May 04, 2010, 01:01:11 pm: @immortal - u answered ur own doubt, lol.
Title: Re: can any1 solve this maths question.
Post by: immortal on May 04, 2010, 01:07:06 pm: Quote from: A@di on May 04, 2010, 01:01:11 pm
@immortal - u answered ur own doubt, lol.
I actually got da ans today,& sme told da ans 0.107 waz wrong, dats y...
Title: Re: can any1 solve this maths question.
Post by: Igcseboy on May 04, 2010, 06:19:06 pm: Quote from: immortal on May 04, 2010, 12:56:50 pm
I got da ans.
3^x+2=3^x+3²
3^x*3²=3^x+3²
9*3^x=3^x+9
9*3^x-3^x=9
3^x(9-1)=9
3^x*8=9
3^x=9/8
x=ln(9/8)/ln3
x=0.107(3 s.f)

It cud also b done using iteration.

how did u get (9-1)????
Title: Re: can any1 solve this maths question.
Post by: dlehddud on May 05, 2010, 08:24:11 am: It's cos he factorised $3^x$ out of the equation to get $3^x$ (9-1)