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April 8th, 2017, 06:11 AM  #1 
Newbie Joined: Mar 2017 From: leuven Posts: 18 Thanks: 0  how did they come to the final step of this equation?
0.2tÂ²+1.2t+3.2 = 3.75 <> 0.2tÂ²+1.2t0.55=0 <> t=0.5 or t=5.5 how did they get to that last step? I tried a lot of things, but nothing gave me those values. Does anyone have any idea how they went from 0.2tÂ²+1.2t0.55=0 to t=0.5 or t=5.5? Last edited by skipjack; April 8th, 2017 at 06:32 AM. 
April 8th, 2017, 06:27 AM  #2 
Math Team Joined: Jul 2011 From: Texas Posts: 2,549 Thanks: 1259 
$0.2t^2+1.2t0.55 = 0$ multiply every term by $100$ to clear the decimals ... $20t^2  120t + 55 = 0$ factor out $5$ from every term ... $5(4t^2  24t + 11) = 0$ factor the quadratic ... $5(2t  1)(2t  11) = 0$ $t=0.5$, $t= 5.5$ note you can also get out your calculator and use the quadratic formula with the original equation ... 
April 8th, 2017, 06:40 AM  #3 
Global Moderator Joined: Dec 2006 Posts: 17,177 Thanks: 1285 
The equation is equivalent to (t  0.5)(0.2t  1.1) = 0, or 0.2(t  0.5)(t  5.5) = 0 if you prefer, so one of the factors is zero.

April 12th, 2017, 11:32 AM  #4  
Newbie Joined: Mar 2017 From: leuven Posts: 18 Thanks: 0  Quote:
i think they used the quadratic formula, which is a formula i know (didn't know its name though good to know that for the future). I'l definitly take a look at the other way to solve it Also sorry for the late reply, i moved location and have been slacking off with my math training for a few days. but today i'm on it again.  

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