Find the radius and centre of the circle given x^2+4x+y^2+2y=20

Complete the square:x2+4x gives (x+2)2-4y2+2y gives (y+1)2 -1Therefore,(x+2)2-4+(y+1)2 -1=20Rearranging gives:(x+2)2+(y+1)2 =25Comparing to the standard equation for a circle:(x-a)2+(y-b)2 =r2Means the radius = 5 (sqrt(25)) and the centre of the circle is (-2,-1)

Answered by Stanley C. Maths tutor

3372 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Solve the simultaneous equations - x+y=2 and 4y^2 - x^2 = 11


Solve the equation 7^(x+1) = 3^(x+2)


What is the equation of the curve that has gradient dy/dx=(4x-5) and passes through the point (3,7)?


A curve has the equation 2x^2 + xy - y^2 +18 = 0. (1) Find the coordinates of the points where the tangent to the curve is parallel to the x-axis.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences