• November 13th 2007, 08:36 PM
tazrulz99
Hi there,

Can someone please show me how to solve the following equation:

5^x + 25^(2x) = 150

Any help will be greatly appreciated,

Cheers
• November 13th 2007, 09:26 PM
janvdl
Quote:

Originally Posted by tazrulz99
Hi there,

Can someone please show me how to solve the following equation:

5^x + 25^(2x) = 150

Any help will be greatly appreciated,

Cheers

Hmm, just check that you didn't make a typo somewhere, it does look a bit like a hard equation for pre-algebra i would say.

$5^x + 25^{2x} = 150$

$5^x + 5^{4x} = 150$

$Set \ 5^x = k$

$k + k^4 = 150$

$k^4 + k - 150 = 0$

I quickly solved it by drawing a graph (See the attached image)

And it seems the answers are -3,54 and 3.46
• November 13th 2007, 09:34 PM
tazrulz99
.
Ok and from there you solve with logs. Thanks!
• November 13th 2007, 09:46 PM
janvdl
Quote:

Originally Posted by tazrulz99
Ok and from there you solve with logs. Thanks!

Yes because $k = 5^x$

But $5^x$ cannot be equal to $-3,54$

Thus $5^x$= $3,46$

I found: $x = 0,77$