Question

a sphere has radius 3xcm. write down an expression for the surface area of the sphere in terms of x.give your answer in the simplest form

Answer 1

The expression to obtain the surface area of a sphere is

$A=4\cdot\pi\cdot r^2$

If the radius is equal to 3x cm then the expression is

$A=4\cdot\pi\cdot(3x)^2$

square the 3x

$\begin{gathered} A=4\cdot\pi\cdot(3^2)\cdot x^2 \\ A=4\cdot\pi\cdot9\cdot x^2 \end{gathered}$

Simplify the expression

$A=36\pi\cdot x^2$

The expression for the surface area of a sphere of radius 3x cm is:

$A=36\cdot\pi\cdot x^2$