Author Topic: exponential query (Read 597 times) Tweet Share

Thymaster · « **on:** March 16, 2013, 03:24:15 pm »

8e^-x -e^x=2 solve for x

Daenerys Targaryen · « **Reply #1 on:** March 16, 2013, 03:28:37 pm »

$\frac{8}{e^x}-e^x=2$

Let $e^x=a$

$\frac{8}{a}-a=2$

$8-a^2=2a$

$a^2+2a-8=0$

$(a+4)(a-2)=0$

$a=-4$ or $a=2$

But $a=e^x$

$e^x=-4$ or $e^x=2$

$e^x=-4$ - not possibe

$x=log_{e}(2)$

Thymaster · « **Reply #2 on:** March 16, 2013, 03:46:43 pm »

but why is it a^2

Homer · « **Reply #3 on:** March 16, 2013, 03:47:16 pm »

Quote from: HatersGonnaHate on March 16, 2013, 03:28:37 pm

$8-a=2a$

should be $8-a^2=2a$

Quote from: Thymaster on March 16, 2013, 03:46:43 pm

but why is it a^2

$e^{2x}=(e^{x})^{2}$

hence $a^2$

Thymaster · « **Reply #4 on:** March 16, 2013, 03:50:53 pm »

i mean isnt it meant to be a initially instead of a^2 since there in no 2 infornt of e^x

Conic · « **Reply #5 on:** March 16, 2013, 03:53:07 pm »

Quote from: Thymaster on March 16, 2013, 03:46:43 pm

but why is it a^2

Multiplied $\frac{8}{a}-a=2$ by a which is $8-a^2=2a$ .

Daenerys Targaryen · « **Reply #6 on:** March 16, 2013, 03:53:22 pm »

Woops typos ill edit it

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Author Topic: exponential query (Read 597 times) Tweet Share

Thymaster

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