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curve y axis

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curve y axis

by pappueshwar » Mon Mar 12, 2012 8:43 am
Does the curve (x-a)^2 + (y-b)^2=16 intersect the y-axis ?

(1) a^2+b^2>16
(2) a=|b|+5


OA IS B

please assist i just dont know how to solve this problem ..
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by kul512 » Mon Mar 12, 2012 12:51 pm
(x-a)^2 + (y-b)^2=16 is a circle with its center on (a,b) and radius 4. If this circle is to cut the y axis then y co-ordinate of its center must be less than the radius of the circle.
i.e |a|<4, so question is asking is |a|<4

A. this will not give any information about a alone. So this can no be sufficient.
INSUFFICIENT

B. a=|b|+5
|b| will be always non-negative so |b|+5>=5
So a is always greater than 5, i.e. a>5 so this option sufficient information to tell that the
circle will never cut the y axis.
SUFFICIENT

Answer B
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