Which of the following is the volume of the solid obtained b

Which of the following is the volume of the solid obtained by revolving the region bounded by y = x3, x = 1, x = 2 and y = 0 around the x-axis. 127 pi/7 62 pi /5 186 pi 120 pi/7 128 pi/7

Solution

consider a disc of thickness dx at a distance x

: dv = (x⁶ )dx

: dv = x⁷ /7   from x = 1 to x=2

: v = (/7)[ 2⁷ - 1 ]

: v = /7 [ 127 ]

v = (127/7)

a) is the correct option !!!