If real numbers x and y satisfy ( x + 5 ) 2 + ( y − 1 2 ) 2 = 1 4 2 , then what is the minimum value of x 2 + y 2 ?
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Solution outline:
The equation can be visualized as a circle centered at ( − 5 , 1 2 ) and having radius 1 4 . So x 2 + y 2 is clearly the square of the minimum distance of the circumference of the circle from the origin which is ( 1 4 − 1 3 ) 2 = 1 .
I first answered 2 7 ... :P
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27 is the maximum of x^2 + y^2.
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Yea, that's why I first answered that. Then, I realized my mistake and answered 1.
Damn, me too. Gotta hate it when I don't read things carefully...
never mind!
Me too .I misread minimum for maximum
I think the circle's centre is (-5,12).
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a bit of typing mistake may have occurred.
Can it be done using distance formula?
Put x + 5 = 14cos(theta) and y - 12 = 14sin(theta) Thus, x^2 + y^2 = 196cos^2(theta) + 25 - 140cos(theta) + 196sin^2(theta) + 144 + 336sin(theta) = 365 + 336sin(theta) -140cos(theta) Thus, minimum value = 365 - 364 = 1
Yes I like your method. It would be better if you use LaTeX :)
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Haha! Thanks and sorry for the inconvenience. :)
sorry , but how did you find 364 ????
Get the equation of the line containing the origin (0,0) and the center of the circle (-5,12)
Get the solutions (intersection) of the Circle and the line.
There will be two solution, but use only the coordinate near the origin.
( 5/13 , -12/13) --- this is the solution
x^2 + y^2 = (5/13) ^ 2 + (-12/13) ^ 2 = 1
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Consider a circle x 2 + y 2 = c 2 .
The distance of the point of intersection of this circle with the given circle from the origin gives the value of x 2 + y 2 , i.e., c 2 . It can be easily seen from the figure that the point of intersection of the blue circle with the given circle gives the minimum distance from the origin.
The distance of ( − 5 , 1 2 ) from the origin is 1 3 and the radius of the given circle is 1 4 . So, radius of the blue circle, i. e., c is 1 . So, minimum value of x 2 + y 2 is 1 .