Answers

2014-10-29T20:17:51+08:00
Use the distance formula, and you'll have:
d^2 =  {(x_2-x_1)^2 + (y_2-y_1)^2}
(2√5)² = (2-x)² + (3-1)²
20 = 4 - 4x + x² + 4
x² - 4x + 8 - 20 = 0
x² - 4x - 12 = 0 
(x-6)(x+2) = 0
x = 6, x=-2
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