It would be 1+1 and that would be 2 so you are welcome
We are concern about the vector (x-x0, y-y0, z-z0)
equaling to 5.
This happens
when √(x-x0)^2 + (y-y0)^2 + (z-z0)^2 = 5
Square
both side:
(x-x0)^2
+ (y-y0)^2 + (z-z0)^2 = 25 , a sphere
Which you will
recognize as a circle of radius one centered at (x0, y0, z0)
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The left hand side of the equation is a difference of two squares and may be factored out as follows,
(x - 4)(x + 4) > 0
They may be individually taken as,
x - 4 > 0 ; x > 4
x + 4 > 0 ; x < -4
Thus, the answer to this item is letter A.
