SOLUTION: the radius, r, of a circle has been increased by k. both r and k are measured in the same units. write a formula for the area of the new circle . expand and simplify r= r+k A=p

Algebra ->  Equations -> SOLUTION: the radius, r, of a circle has been increased by k. both r and k are measured in the same units. write a formula for the area of the new circle . expand and simplify r= r+k A=p      Log On


   

Question 769894: the radius, r, of a circle has been increased by k. both r and k are measured in the same units. write a formula for the area of the new circle . expand and simplify
r= r+k
A=pi*r^2
= pi*(r+k)^2
=pi*(r^2+2rk+k^2)
is this correct or something's wrong?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Original radius, r.
Increased radius, r+k.

For this situation, because you are not writing some kind of computer code, do NOT say r=r+k.

A%5B0%5D=pi%2Ar%5E2
The subscript is for original or initial.

A%5Bn%5D=pi%2A%28r%2Bk%29%5E2
The new area when radius increases by k.

But your work in your last two steps is good. The new area IS pi%2A%28r%5E2%2B2rk%2Bk%5E2%29.
You just cannot say A=pi%2Ar%5E2=pi%2A%28r%2Bk%29%5E2 because it is wrong.