Sunday, 20 July 2014

algebra precalculus - Solving the equation 11x26000x27500=0, preferably without the quadratic formula



I obtained this form while solving an aptitude question.



3000x50+3000x+50=11



I changed it into quadratic equation




11x26000x27500=0



but I don't know how to solve it.



I can't find two factor for 303500 that sums to 6000 or when I use formula the numbers become huge...
Without using calculator
how to solve it? is there any other simple way to solve [other method]? [or finding factor] I'm a beginner in math. Please explain your answer for me.


Answer



There isn't any standard, guaranteed method apart from the quadratic formula to solve a quadractic equation. However sometimes there are "ad-hoc tricks" which might help you get one root.




The RHS of the equation is an integer; You might suspect that an x such that both the terms on the LHS are integers might be a root (this does not have to be true at all, but it's not bad to try).



Also since x50 and x+50 differ by 100, you want a number y such that both y and y+100 divide 3000. Noticing that 500 and 600 satisfy this gives x=550 as a root.



Using this, you can find the other root quite easily to be x=5011 since the product of the roots is 27500/11.


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