Difference between revisions of "2010 AIME II Problems/Problem 7"

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x(x+6i)(2x-4-6i), the imaginery part is: 6x^2-24x, which is 0, and therefore x=4, since x=0 don't work,
 
x(x+6i)(2x-4-6i), the imaginery part is: 6x^2-24x, which is 0, and therefore x=4, since x=0 don't work,
 
so now, <math>x_1 = 4, x_2 = 4+6i, x_3 = 4-6i</math>
 
so now, <math>x_1 = 4, x_2 = 4+6i, x_3 = 4-6i</math>
 +
and therefore:
 +
<math>a=-12, b=84, c=-208</math>, and finally, we have |a+b+c|=|-12+84-208|=136.

Revision as of 11:58, 3 April 2010

set $w=x+yi$, so $x_1 = x+(y+3)i$, $x_2 = x+(y+9)i$, $x_3 = 2x-4+2yi$. Since $a,b,c\in{R}$, the imaginary part of a,b,c must be 0. Start with a, since it's the easiest one to do: $y+3+y+9+2y=0, y=-3$ and therefore: $x_1 = x$, $x_2 = x+6i$, $x_3 = 2x-4-6i$ now, do the part where the imaginery part of c is 0, since it's the second easiest one to do: x(x+6i)(2x-4-6i), the imaginery part is: 6x^2-24x, which is 0, and therefore x=4, since x=0 don't work, so now, $x_1 = 4, x_2 = 4+6i, x_3 = 4-6i$ and therefore: $a=-12, b=84, c=-208$, and finally, we have |a+b+c|=|-12+84-208|=136.

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