Shadowing Posted July 4, 2012 Share Posted July 4, 2012 Hey guys im trying to figure out how to do this problem backwards $x = pow(1407, .5) / 25; this equals 2.5 what I really want to do is find the number 1407 by knowing what x is so the equation i need to figure out is like 2.5 = pow(x, .5) / 25; anyone know how to do this? im really stuck here lol Quote Link to comment https://forums.phpfreaks.com/topic/265189-doing-this-problem-in-reverse/ Share on other sites More sharing options...
Pikachu2000 Posted July 4, 2012 Share Posted July 4, 2012 $x = pow(1407, .5) / 25; this equals 2.5 Ummmm, no it doesn't. You won't get the right result starting with the wrong values. Quote Link to comment https://forums.phpfreaks.com/topic/265189-doing-this-problem-in-reverse/#findComment-1359102 Share on other sites More sharing options...
xyph Posted July 4, 2012 Share Posted July 4, 2012 Hahaha, this is an epic math failure . First, your initial calculator punching is wrong, as pointed out by Pikachu2000. Second, you're not reversing the equation, you're solving for a different unknown. It's the same equation, just with a different isolated value. A number to the power of 1/2 is the same as taking the square-root of that number. So, if 2.5 = sqrt(x) / 25 then 2.5 * 25 = sqrt(x) and finally (2.5 * 25)^2 = x Quote Link to comment https://forums.phpfreaks.com/topic/265189-doing-this-problem-in-reverse/#findComment-1359122 Share on other sites More sharing options...
Shadowing Posted July 5, 2012 Author Share Posted July 5, 2012 lol guys opps my bad i gave the wrong numbers xyph you are awesome seriously thank you Quote Link to comment https://forums.phpfreaks.com/topic/265189-doing-this-problem-in-reverse/#findComment-1359266 Share on other sites More sharing options...
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