Question

Does the equation x² - 4x + y2 = -3 intersect the x-axis?

a. yes, because the center is on the x-axis.

b. no, because the center is at (2,0) and the radius is 1

c. no, because the circle is entirely in the first quadrant.

d. yes, because the center is at (-2,0) and the radius is 3.

Answer 1

Answer: a. yes, because the center is on the x-axis.

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Step-by-step explanation:

The x intercepts always occur when y = 0.

Replace y with 0 and solve for x

x^2-4x+y^2 = -3

x^2-4x+0^2 = -3

x^2-4x+0 = -3

x^2-4x = -3

x^2-4x+3 = 0

(x-3)(x-1) = 0

x-3 = 0 or x-1 = 0

x = 3 or x = 1

This shows that the x intercepts are located at (3,0) and (1,0). Refer to the diagram below. The diagram shows that the roots are at points A and B. The center is the midpoint of A and B. The center is also on the x axis.

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Here's another approach:

The general template of a circle is (x-h)^2 + (y-k)^2 = r^2

Let's complete the square of the original given equation to get it into that template form above.

x^2 - 4x + y^2 = -3

(x^2-4x) + y^2 = -3

(x^2-4x+4) + y^2 = -3+4 ... add 4 to both sides

(x-2)^2 + y^2 = 1

(x-2)^2 + (y-0)^2 = 1^2

The equation is now in the template form mentioned earlier. The center is at (h,k) = (2,0) which is on the x axis.