Kate M. answered • 04/28/14

Expert Ivy League Tutor for LSAT, GMAT, GRE, and SAT/ACT

Kate M. answered • 04/28/14

Tutor

5.0
(280)
Expert Ivy League Tutor for LSAT, GMAT, GRE, and SAT/ACT

Hi Zach,

The equation for a circle centered at the origin on a coordinate plane is

x^2 + y^2 = radius^2

so, we can tell from your original equation that the radius of the circle is 7, because 7^2 = 49.

Just like moving a parabola using the y=x^2 equation, if we change the circle equation to

(x-1)^2 + (y+2)^2 = 49

we move it 1 unit to the right, and two units down. So since the center started at (0,0) the new center will be (1,-2). Hope this helps!

Kate

Francisco E. answered • 04/27/14

Tutor

5
(1)
Francisco; Civil Engineering, Math., Science, Spanish, Computers.

I would say that the equation of a circle with center at (h,k) is (x-h)^2 + (y-k)^2 = r^2. In our case h=1 and k equal to -2, the center will be at (1,-2)

CHECK!!!!!!!!!!!!!!!!!

The standard form for a circle of radius seven centered around the origin is xsquared plus y squared equals the radius squared (49). Why does this work? Let's test a few points Off the x,y axis: (7,0) (-7,0) ((0,7) (0,-7)

These are the four points of the circle intersecting the two lines dividing the circle in half. So we need values of x and y that create that same (0, +/-7) (+/-7,0)

In this case we find x=1 and y=-2 the intersection for the two lines is the center.

Hope that helps,

Deanna

Ask a question for free

Get a free answer to a quick problem.

Most questions answered within 4 hours.

Find an Online Tutor Now

Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.