Math Module 2 (Hard) Question 9

Circle $A$ in the $xy$-plane has the equation $(x-3)^2+(y+2)^2=4$. Circle $B$ meets Circle $A$ at a point on the $x$-axis and has the radius that is twice the radius of Circle A. The equation defining Circle $B$ in the $xy$-plane is $(x+a)^2+(y+b)^2=R$, where $a$, $b$, and $R$ are constants. What is the value of $a+b+R$?
Answer:
Answer:
9

Explanation

The correct answer is $9$.

Use the given equation of circle $A$ and the standard equation of a circle to write the equation of circle $B$ and, therefore, find $a+b+R$.

✨ Expert's Tip ✨

If two circles meet at an axis, they share one same coordinate.

    About Exxcel

    Exxcel was established by a team of dedicated educators and experienced test writers who share a common goal: to equip students with the tools they need to excel in their exams. As an online Digital SAT® test preparation platform, our mission is to empower students to realize their full potential through mentorship and the delivery of high-quality, accessible education.

    College Board® is a trademark registered by the College Board, which is not affiliated with, and does not endorse, this website. Exxcel is unaffiliated with College Board® and do not have access to College Board's proprietary data.