Question 658983
Do it like this:
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Find all of the points on the x-axis which are 4 units from the point (-1,1)
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The vertical distance = 1 (1 unit above the x-axis)
The hypotenuse = 4
Distance on the x-axis from x = -1 is
{{{d = sqrt(4^2 - 1^2) = sqrt(15)}}}
---> (-1-sqrt(15),0) and (-1+sqrt(15),0)