Question

A lawn service company offers services within an 20 mile radius of their office When the service area is represented graphically with the office located at (0,0) the equation that represents the service area is

• A. x${}^2$+y${}^2$=20
• B. x${}^2$+y${}^2$=40
• C. x${}^2$+y${}^2$=400
• D. x${}^2$+y${}^2$=4000
• E. none of these

Answer 1

Answer: (C)

x${}^2$+y${}^2$=400

Clearly the service area is circle with center (0,0) and radius 20 mile.
Therefore the equation of service area is
$(x-0{)}^2+(y-0{)}^2=(20{)}^2$
i.e. $x^2+y^2=400$
Option C is correct.