I have formulas written down for volume using rotation around certain axis'. How do I know what to do with d? Do I aways convert to y terms if it is about the y axis?

JaLy Volume 4= TTS 2 ( x ) To [ b [ f ( x ) ] = d x 9 = e d limits f ( x ) = g( x ) TO S [$2 (x ) - 92 ( x ) ] dx O out yaris to Sb [(f ( x ) - d2 ) + ( g (x )-db ) ]dx