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2 years ago

4. Stella says the equation x^2−8x+y^2+2y=5 has a center of (4,−1) and a radius of 5. Is she correct? Why or why not?

Mathematics

1 answer:

Ostrovityanka [42]2 years ago

8 0

<h2>Stella is correct about center and wrong about radius </h2>

Step-by-step explanation:

Equation of circle with (h,k) as center and radius r is given by,

(x-h)²+(y-k)² = r²

Here equation is

x²−8x+y²+2y=5

Changing in to (x-h)²+(y-k)² = r² form

x²−8x + 16 - 16 +y²+2y+1 - 1=5

(x-4)² - 16 + (y+1)² -1 = 5

(x-4)² + (y+1)² = 22

(x-4)² + (y+1)² = 4.69²

Center is (4,-1) and radius is 4.69

Stella is correct about center and wrong about radius

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Option D (The student should have used as the slope of the perpendicular line.) is correct.

Step-by-step explanation:

We need to identify the error that the student made in finding equation of the line that passes through (-8,5) and is perpendicular to y = 4x + 2

The slope of the required line would me -1/m because both lines are perpendicular.

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$y-5=-\frac{1}{4}(x-(-8))\\y-5=-\frac{1}{4}(x+8)\\y-5=-\frac{1x}{4}-2\\y=-\frac{1x}{4}-2+5\\y=-\frac{1x}{4}+3$

This is the correct solution.

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So, Option D (The student should have used as the slope of the perpendicular line.) is correct.

Keywords: Equation of line using Slope

Learn more about Equation of line using Slope at:

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