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Which of the following lines is tangent to circle x^2 + y^2 = 8?

0 votes

(a) x + y = 2 
(b) x + y = 4 
(c) x + y = 6 
(d) x + y = 8 
(e) None of the above 

explain why please.

asked Aug 1, 2015 in PRECALCULUS by anonymous
reshown Aug 1, 2015 by bradely

1 Answer

0 votes

Step 1:

The circle equation is .

The line equations are , , image and image.

Let the tangent line equation be image, where image is a positive integer.

Substitute in to form a quadratic equation in image.

image

image.

Step 2:

Find the discriminant of the quadratic equation to obtain image.

Since represents tangent line, .

Substitute image and image in image.

image

.

Susbtitute in the line equation image.

image

The tangent line equation to the curve is .

Solution :

The tangent line equation to the curve is .

Option (b) is correct.

answered Aug 1, 2015 by Sammi Mentor
edited Aug 1, 2015 by Sammi

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