The expression to obtain the surface area of a sphere is
[tex]A=4\cdot\pi\cdot r^2[/tex]
If the radius is equal to 3x cm then the expression is
[tex]A=4\cdot\pi\cdot(3x)^2[/tex]
square the 3x
[tex]\begin{gathered} A=4\cdot\pi\cdot(3^2)\cdot x^2 \\ A=4\cdot\pi\cdot9\cdot x^2 \end{gathered}[/tex]
Simplify the expression
[tex]A=36\pi\cdot x^2[/tex]
The expression for the surface area of a sphere of radius 3x cm is:
[tex]A=36\cdot\pi\cdot x^2[/tex]
